If you are going from a 351M to the 400 it is a direct swap. If you are going from a 351W to a 400 it won't be, different trans, exhaust, motor mount's and so on. Why not just find a 429 or 460 a do a REAL swap.
i agree with ranger429 > . find a 429/460 and do a real swap. the only difference between the 400 and 351M is the crank and pistons. The 351W has the same trans bolt pattern as a 302. Didn't know you were here Ranger429. I just came across this site. a lil bit different. The swap to a 351W will amount in exaust, motor mounts, & trans. a 429/460 would go right in and you would only have to change the motor mounts.