[UnexplodedCow]

You can't use an LX head on an HO bottom end without changing to LX pistons, or else you machine the LX combustion chamber into a hemi, which is a bit of a waste since it's a small port, small valve design. The compression between 87 and 90 are the same. The only difference will be the 90 having a roller cam setup.

The LX head could possibly be machined, but the intake manifold is different (you'd have to use a 2nd gen intake) than the HO type.

 

[UnexplodedCow]

You also need the LX intake...it will NOT bolt to an HO head..bolt patterns, gaskets are different, water port is different. The bolt patterns are close, but it's really the port location that makes everything not work. I've tried...believe that.

 

[UnexplodedCow]

LX and GT blocks are identical in every way. They use all the same parts, except for pistons. The difference between HO and CFI is in the head/intake.

You could also look at using a 2nd gen intake for the CFI head, but you're still stuck in the small port/small valve land.