I have a lm7 and I have 799 heads trying to get. To 11.1 c/r should I get dome pistons or flat tops and should I bore it to a ls1 5.7 I have a 1984 z28 that will only see the track

 

799 heads on an LM7 will drop compression and you'll lose power over stock heads.

You can put some stock 4.8 pistons, or gen 4 5.3 rods and pistons in your LM7, with ported 862/706 heads that are milled, and get 11:1 fairly easily and it'll make a good bit more power than a stock LM7 with 799s.