the blocks are the same, you could keep it 16V with some work if you wanted.
stu
The block is the same, but I understand the pistons may not be "non-interference" enough in an 8-valve for a 16-valve head, so you would need to use the 16-valve pistons (and maybe the connecting rods -- again, which may be tougher than the 8-valve's). The 8-valve crank may be different -- I understand that the 16-valve crank is better-balanced.
Are we starting to see a pattern here?
I'd either wait for a 16-valve truck to appear at a salvage auction (or in the classifieds/Thrifty Nickel) or stick the 8-valve engine/harness/ECM in your truck.
Grammer tip 'O the day:

8-valve's = Possessive
8-valves = plural