I have a 305 LG4 83 Pontiac Firebird with a edelbrock carb and my friend is selling ported -88 305 TPI heads. Is there any differences between those heads that would make direct swap not possible? Water passages etc? Should I use -83 or -88 head gaskets?

 

The '87-up heads have two intake manifold bolts (each side) that are at a different angle than the others. In order to bolt them up, you'll either need to elongate those holes in your manifold, or get an intake intended for '87-up style.

Also, '88-up used self-aligning rocker arms, meaning you can't use your '83 parts. You'll either have to use the rockers that came with the '88, or buy self-aligning parts.

Head gaskets will be identical. Your '83 will have dished pistons, so to keep the compression up, use a steel shim gasket like the factory did. I used FelPro 1094, which have a compressed volume of 3.2cc, vs. the normal 9cc compressed volume of a typical composition gasket. They ain't cheap, but every little bit helps.

 

As he saind, the inatake manifold holes are at a different angle, but with a die-grinder you can shift the hole angle... CAREFULLY!. I bought some 89 GTA heads that had a lot of machine work dome to them... good deal, but without the work dome to them it would have been a waste of Moo-lah... Some Vortecs would serve the cause much better for the money, but require a new intake, and an EGR relocation kit from SD.