Well,
There are gonna be many thing you'll need to watch out for.
First off, you'll need new engine mounts, exhaust manifolds or headers, header pipe, radiator hoses, accessory brackets, p/s hoses....
Then you'll have to look at what that tranny came out of. Ford has three different tranny bolt patterns for Classic Cats. Small block(221-351W, 351C), tall block (351M/400M, 429 & 460), and FE (352, 360, 390, 427, 428). Even if you have the right bellhousing bolt pattern, there are a couple of different tailshaft housings for the differing style of tranny mounts. Then there's the linkage arm on the tranny.... Are you sure your current tranny is a C-4 and not an FMX? They look somewhat similar. C-4 usage usually stopped with 302s. 351 cars are usually FMX or C-6. Some applications even use FMX and C-6s on 302s. If you do have an FMX, it has a bolt-on bell housing. Yes, so do the C-4s, but I don't know of any FE-C4 bellhousings. There are, however, FE-FMX bellhousings. Anyway, you have the car there and can look, I can't from here. Sorry if you already know all of this.
Do you have the correct tranny flex plate and torque convertor for the FE-C6?
You will have to either obtain the correct driveshaft or cut down yours to fit. You have the right tranny slip yoke?
How about the correct floor shift trans linkage?
Speedo cable?
Throttle cable?
Downshift rod?
Since the FE is almost 100lbs heavier than the Cleveland, you might want to upgrade the front springs.
Long story short. It will be expensive and a lot of work.
I had a 429CJ that I had picked up for a song ($200). I was going to put it in my 73 Cougar in place of the 351C-4V. After adding up the costs, I decided to stick with the Cleveland!
Good luck
