Ok I have a 79 f150 4x4 short bed with 351m and c4 trans I have 78f250 parts truck 2x4long bed with 390 c6 I want to put 390 in 79 4x4 I have read the trans won't mount up so what do I do can I can't bell housing or what looking for ideas adapter plate maybe ?

 

You dont really have a parts truck, it sounds like you have 2 trucks.

There is going to be expensive fabrication work between:
351-390
C4-C6
F150-F250
2WD-4x4

Your cheapest, easiest, and most reliable choice is to rebuild the 351 and upgrade the cam, heads, intake, carb, add headers, etc.

 

Your right I have two complete trucks I want 390 it hAs very low Miles I would think buying used c6 for 390 4x4 be cheaper than rebuilding 351.

 

you dont have a c-4 in the 79 4x4 either. It has to be a c-6. Still wont bolt up to the 390 though. By the time you buy a tranny that will bolt up to the 390 and do all the other alterations necessary you should be able to build a good 351m/400

 

No 351M in a F100/350 came with a C4, the only A/T available was the C6.

1976 was the last year 360/390 engines were available in F100/350's, but 4WD's were only available with 360's.

 

Ok guy I'm not sayn I'm not grateful for replies but we are getting of subject. I didn't ask if I should rebuild 351 or not. I asked how to make it work in truck. So please let me know what can be done a used c6 can be had for well under 500 bucks.

 

Well, you would need a C6 4x4 trans with the FE bell housing (totally round, not trapezoid top). Also, you would need the engine towers for the 4x4 truck for the 390. The other than that, it should be fairly straight forward in concept. As they said, could be pricey with all of the little things that come up. The the FE automatic should have the NSS switch in the steering column. The other may have on trans. Though, this can be rectified with simple wire splicing. Driveshafts should require no modification.

 

Also you will need the 390 to be a rear sump oil pan.

 

Well I think I'm going to hold off of the swap it runs fine I just want bigger better motor. Maybe some day