Since FE big blocks were installed from the factory, I do not forsee many problems for you. A 351W is basicly a stroked 289/302 with a taller Deck hight. Any demension differance should be at the top end,but still won’t be as wide as an FE(390). You may need you use accessory brakets from the 351W. Exhaust Manifolds will sit a little higher and farther out. Should not be a hard swap.
I did this with my sons '68. There are Hedman headers that are designed for this swap, and we used them. The front brackets all need to come from the 351. The radiator fan did not line up well with the shroud from the 302. You might be able to use a '69 351 shroud. Do you have the 24" wide radiator?
I am running an aftermarket aluminum radiator. I think it is 24 inches. I am mostly worried about the increased height of the motor and the headers clearing power steering parts. I have the drop bracket on the cylinder. Also, as it sits right now with the 289 in there, the clutch z bar comes very close to the header. I do not see it clearing with the taller deck height of the 351. I will be using the same headers I have on there now until the engine break in time and then I have some ceramic hookers that are to accommodate the 351.
How is the carb to hood clearance? I have a Edlebrock RPM plus manifold for it but will be using the low profile oval cleaner.
There are a lot of variables in there. Our car is an automatic so I can’t comment on the clutch issues. We also used the Hedman shorty headers that are designed for the swap. The hood clearance will be tight. I have read that the RPM air gap is a no go, but the regular RPM fits, and then I also read that the two are supposed to be the same so again, I don’t know what to tell you. I think that you may have to just wing it a bit. The good news is that it certainly is possible to put the 351 in, but finding some one with exactly the same set up might be really tough . I think the time to find out if the Hookers will fit is when you have the engine on the hoist. Good luck!
Yeah it will show up upon install. I think I might get a set of shorties on hand just in case. I did a 351 in a 67 stang but it was factory intake and exhaust manifolds. By the way it was a low mileage 4bbl out of a wrecked 69 Mach 1 and it made that 67 fly! 290 HP my butt!
Shorties make it go really easy, and they allow you to eliminate the drop bracket too.
The 351W fan is the same height as the 289
Use the 289 mounts
You can get the alternator and PS adapters from the Bronco forum
Use the front cover, water pump, pulleys, harmonic balancer, flywheel from the 289. Both engines balanced the same.
Performer RPM is the tallest intake you can use without cutting the hood.
Headers, I used Hooker 6901, Worked on 302 as well as the 351W, auto and 4sp.
Lots posted on this swap back on MCnet. (Unless it was deleted)
Info: Later 351W engines ('89- Up) have the clutch Pivot-Ball Mount cast, But not drilled.
Here’s another tip when performing this swap. When using a block that came from a vehicle with a rear sump, the dipstick hole on the driver’s side of the block needs to be plugged. Although, I’ve heard of people using dowels, globs of RTV and freeze plugs to plug the hole with mixed success, the most secure way to plug the hole is with an 1/8" NPT tap and plug.
And the last few years of the 351W’s didn’t even have the boss cast in.
thats what I have done on late model blocks. 1/8"npt tap and plug works everytime!
I used a small ‘freeze-plug’ type cup plug, and some good Permatex on it and have no leaks. Of course, I had to plug the dipstick hole in the universal replacement timing cover and not the block since my application uses the rear sump pan… Even trickier trying to tap that plug into place without cracking the aluminum cover… 
I know this post is old, but I need help. Okay I have a 1968 Cougar XR7 came with 302, may son-n-law had a 351W 1969, we were going to put it in his old mustang, he sold his mustang. SO I purchased the motor from him, had it built. put it in the car today, and I hooked a stage two AOD behind it with a 2500 stall. anyways its in there, Going to have to build a custom transmission support, I get that. my issue is this. not even a factory exhaust manifold will fit on the drivers side. Passenger side is humpty-dory. TO me the engine needs to come forward about an inch. do they make special engine mounts to do this? what have I got my self into? Even the long header fit on the passenger side. but not on the drivers side. Does 302 and 351 use same distributor shaft? Well if you have been there and done this please help me out all you can.
I know this is another’s post, but I need some help, I have a 68 cougar xr7, pulled the 302 out, put in a 351 slightly modified, AOD transmission, my passenger side header fits, my drivers side will not, nor will a factory 351 manifold. so what is the engine bay width so I can check for sagging? Is there certain type motor mounts I should use? Need help here, thanks for any and all advice.
I had to jack up my engine to make the driver side header work. I’m running the FPA headers FWIW. I just used 302 motor mounts. I THINK all the mounts were the same during that era.
I’m running adjustable engine mounts with FPA headers with no issues. Had to run the mounts mainly to get my roll center as low as I can, and to clear the hood. I have a Super Victor JR Intake which is very tall. 351w (408) in a 67 Cougar.
http://extremecustomparts.com/i-8550476-adjustable-motor-mounts-for-small-block-ford-mustang-cougar-falcon-289-302-351-347-408-427-stroker-free-shipping.html
https://cccforum.discoursehosting.net/t/a-pair-of-sevens-and-a-1-2/1073/1
On my 68, I’m running stock 302 mounts and 351W headers I ordered for a 69. But I don’t run stock steering. I DID have to “adjust” the collectors from hitting the C6 trans. Nothing major though.
Also, I forgot to add:
Ron Morris also has the adjustable motor mounts but a little more $$$
He has the trans mount for AOD as well if you don’t want to fab your own.
http://www.ronmorrisperformance.com/miva/merchant.mvc?Store_Code=RMP&Screen=CTGY&Category_Code=AOD
I used Hedman 88650 Headers with a '69 351 in a '68 XR7 with power steering. No issues at all. http://www.summitracing.com/parts/hed-88650/overview/year/1968/make/ford/model/mustang