90 Jetta engine

I recently purchased two Jettas for a very good price.
One '87 and one '90. The '90 has a 1.8L MFI/FI 8 Valve engine, with a cracked head. I'm new to VW's and I was wondering if the 16 valve head would fit on this block, and if there would be any additional parts needed, or ECU differences.
I was also wondering if anybody knows of a site with this sorta info on it.
Thanks