Your '91 won't have EGR or a cam sensor. The 1993 may have one or both (depending on when in 1993 it was built and if it was a California vehicle).
So, at the most, you'll use your old exhaust manifolds, the cover from the top/back of the block (or leave cam sensor in) and the upper plenum (egr).
Oh yea, use your 1991 engine wireing harness as they will be different from 1991 to 1993.
~Mark