You most likely have GE30E heads which were 5.5:1 Compression. They were replaced by 10A4209 also 5.5:1. My UTS has one of each and runs fine.
The more desirable heads would be the GE30M or GE30Z or 10A4210 which were 6.95:1 Compression Ratio. If you are changing both heads, you might want to consider upgrading - just make sure you have the correct Head Bolts and Pushrods. The Head height for the GE30E was 5 inch but the GE30M and GE30Z were 4 17/32 inches.