This is generic info from other swaps, I haven't swapped anyhing into a MN-12 body.
302-351W mounts, bellhousings and timing cover are all the same bolt patterns. The 351W oil pan is deeper so often a 1/2" spacer is required to lift the motor to clear the oil pan from any crossmember. This can be done a simply as using washers between the motor mount and the block (2 bolts, each side).
302 and 351 heads are near twins so the exhaust flange is the same. 302 headers will bolt onto a 351W and occaisionally will work with the chassis they are desined for. Any problems are with the added height and width of the 351W. This used to work fine on many low headers for older (60s-70s) Mustangs and such but I can't say for the MN12. Exhaust manifolds are usually an easy swap, requiring only a spacer to widen the Y-pipe if used.
Steve Best