I'm not certain.
The 460 crankshaft sticks out 1/2" more than the 351M/400 crank in relation to the bellhousing face.

There may be a different flexplate or TC to account for this.

For certain the ring gear needs to be where it needs to be for the starter to engage.

I'm not too well versed in automatics when it comes to this swap.
Hopefully somebody else will chime in.

 

The longer crank stickout is only on the external balance engines. Internal balanced with a 390 flywheel and a M/400 bell will work just fine.
I know there is no change in the transmission for an auto. The flexplate of course is a different part, but I am not sure if anything changes besides the balance weight.

 

Its an '85 460 so definitely external balance.

Idk how Ford made the same starter work if the flywheel/flexplate moved that much during the '79 changeover, but it's good to know.

 

If I understand the above, you have the 460 and 351M motors and trans. I guess that includes the 460 bellhousing still attached?

Use all of the 460 flywheel, clutch, bellhousing, and bolt 351m trans to it. Then convert over to the hydraulic clutch assembly. Or am I still missing something?

 

There's ~1/2" of difference between the flywheel position for an M and a 460. What we don't know is how Ford accommodated that change. Was it all in the bell housing, all in the input shaft, or some in both?

But, if the OP has both setups he can measure the bell housings and input shafts and figure it out.

 

There is no change in the input shaft. The 460's bell is deeper to accommodate the crank stickout and larger diameter flywheel.

 

Right

.... so what happens when you try to use a shallow 351M bell on a 460????

The input shaft bottoms in the pilot bearing, the pressure plate & flywheel hit inside the bellhousing.
...and there's no room for the release arm.

THIS is why L&L make a swap flywheel and clutch.
(Posts 2, 6, 7 &12)

What's so hard to understand?

 

Agreed. The catalog shows that all NP435's took the same input shaft regardless of the engine, both 6 and 8 cylinder. It is listed as "17 helical—2 1 clutch teeth— 10 splines-9" long", So the difference is in the bell housing.

 

Years ago I swapped out my 5.8HO from a 86 f-150 and bought a 69 429 with a heavy duty C6/ case from a station wagon and bought a .010- .010 460 crank for the complete rebuild. Used DOVE ported heads and 1.75- 2.25 stainless valves.
I got all my conversion parts from L&L products to fit all my 351 accessories to the 460. Included were a new rear sump pan, Military grade HD motor mounts, Doug Thorley Nickle plated HD tri y headers all the cad plated brackets for P/S pump, AC mount, alternator mount, a nice remote oil filter set-up and a few things I can't remember cuz it was over 15 years ago.
I DO remember the total package back then was well over a thousand plus bucks.
Soooooo, how bad do you want that high torqin' engine? I would have been better off to get new heads and cam etc for the 351 HO and been happy with that, especially the gas mileage.
The bored out 460 will pass anything on the road but a gas station!
Just my 2 cents.
Bud in Winslow AZ

 

ford put 460 with 4 speeds in 79 rord truck and 77 have both with original equipment the piviot ball for the z bar on the 79 460 bolts to the bellhousing and the one for the frame is easy to make or order and pre 83 ford cab can have all the clutch petal parts needed to useanual clutch the 400 bell housing will work with a 460 done the 400 460 swap several times use a 174 tooth fly wheel and diapham clutch we have 2 pulling truck with 460 and manual trans

 

Only 2wd correct? The 4x4 trucks in the late 70's only got the 400? Which would not matter with the bellhousing.