I have a 390 FE in my 71 f100. Now i have a NP435. I want to know if the c-6 from a 351 will fit my 390 or what do i have to do to make it fit. Is the bell housing separate from the tranny itself? Thanks--Nick

 

Unfortunately no. You will need a C6 from an FE. 352, 360, 390, 406, 428. I changed one of my rigs from man to auto and was not as happy as I thought I would be. Automatics have a slip factor of an average of 15%. This sucks up power, uses more fuel, and lowers your gear ratio by the % of slip. This is why typicly your autos run higher gear ratios (lower numbers) than sticks. Some Folks swear by autos and I thought I was getting to old to shift all the time so I made the change and now I never drive the truck. I have a 79 1ton 4x that I put a 90 7.3 with the 5 speed and I drive that everywhere. After the auto I like the man even with the extra gear. Just my own preference of course. Rick

 

Unfortunately for you, C6 tranny's have an integral bellhousing (not separate). And there are 3 types: Smallblock: 300,302,351W,351C FE Block: 360,390 (many others such as 352,428 as long as in the FE family) Big Block: 351M 400 429 460. Which 351 do you have, if 351W maybe you can find an eager purchaser that wants to upgrade from a C4 (mustang owner,300,302 truck owner). I can buy a used FE type C6 in the Seattle area for as little as $150 from a decent wrecking yard with a short term warranty. I did this with a 3sp to C6 smallblock conversion. I did have some bellhousing leakage from the front seals probably, it worked decent but leaked. The engine went bad, and before I use again I'm going to take the tranny to be rebuilt for $500.