Have a 1978 f150 with the 4.9l t18 4x4. Motor has no compression and needs a rebuild, in the meantime I have a 351m with a c6 sitting in my garage. I want to put the 351m in and marry it to the t18 currently in the truck.

want to confirm that the bell housing are different and will the bell housing on the c6 work on the t18 if swapped with the 351m.

anything else I should also be aware of?

 

Bell on C6 is integral so no soap using it.

You need a bell from a 351m/400.

Unless you need to turn the truck around very quickly I would rebuild the six.

As OEM, the 351m barely made more power than the six but was thristier.

Cooling, exhaust, FEAD, all the little stuff....while you could be slapping new pistons into that six.....

Swerving suggestion.

 

I agree with 85e150, unless time is of the essence, I would rebuild your six...

 

There’s a lot of days I think I’d trade my 460 for a 300 I6. There’s not a snowball’s chance in hades I’m swapping a 351m to replace a 300. Your time, money and truck but I’d do a quality rebuild on the I6.

 

There have been decades that I've wondered what I was THINKING, when I pulled a 400M for a 300 implant.
Yes, I'd never owned a Ford 300. And at the time was running a nice balanced 385 series 429 in my 4x4 Van.
Anyways, I had the rotating assembly for the 300 build Balanced with .040 hyper flat-top pistons.
My guess is the 400 had more torque than the lesser 300. Oh well.

On another CrewCab that I purchased from a logging company, it came from Lowman, Idaho, home of beautiful horses, and Fast Women. hahaha whew, if you've seen some of the cow-girl butts in rocky jeans, the heart would Leap. hahaha
I drove the 400 for over a year with a rod knock, while I freshened up a 400 from a full sized wagon with engine fire.
Ha, the young chap said his dad had it rebuilt,. That was a farce, so very glad I tore it down. Rings were all carboned tight in the piston ring glands. Oil return holes in the pistons were carboned closed. A needed gasture of love, and it woke up.
Once I de-glazed the cylinders, checked bearings, grind valves, check deck and head flatness, and Hello checkered flag.
That 400 ran super great, and no slouch. I liked the 400M. _ _ it was in a '78 F250 CrewCab pickup 4x4, w/ C6.
I looked up the population of Stanley, Idaho, and it was topped at 65 people. I'd say horses out-number women. LoL

 

I tried to read this but I didn’t really end up with a conclusion as to what your main point was or what what engine you think is better. The details of each were pretty . Then there was something about horses

 

And less woman what was he thinking

To the OP the 300 six was used up into the mid 90's IIRC all be it in 87 they went EFI so some changes where made to the blocks but can be over come easy.
The EFI block do not have a fuel pump opening so would need to run electric.
They say the bolt holes are threaded so if you had someway to keep metal out of the block you could open it up.

The other thing is the block side clutch pivot that screws into the block is not drilled or threaded.
This can be done before the motor is dropped into the truck as you would have more room to work.

If you can get the EFI EXH manifolds do so as they flow better than the log manifold on your motor you just need to get the EFI Y pipe and adapt it to your system. If you use the truck in the winter you should heat the bottom of the intake like the log EXH manifold did.
A plate with some hose fittings and run hot water to the bottom and you will be good. I have the hot water heat and used my truck in 20*f day with out issues.

The last would be hot air asst. choke. If your carb choke uses tubes to / from the log EXH manifold you will need a way to do the same.
I used copper tubing and wrapped it around the EFI EXH manifold a few times.
On the 20*f days the choke would not pull off all the way so I wrapped header insulation over the tubing to trap in more heat and that did the trick.

Been running that set up for over 5 years / 28K miles with out issues in my 81 F100.
Dave ----