Hi, I have just sourced an 89 year r5k engine and have the same heads with the casting number KV3 GR E1 on it.

These heads are slightly taller than the 88 year r2j/r4j heads.

If the replacement heads are the same height with the casting numbers ending E2, then I am guessing they are for a r6k late 89 year engine.

I doubt there are any differences.