c-speedracing.com has a pretty good compresson calculator for hondas. u can choose pistons, head gasket thicknes, head, block, etc....i can tell you that the gsr/type r motors have longer rods to compensate their shorter stroke than the ls motors. thus giving the ls its less than ideal rod/stroke ratio. if u use a gsr head over a b16/type r head, expect about a .3 increase in compression. u can expect about the same increase from a 2 layer head gasket too, but your only problem is most are made strictly for b sereis vtec motors. when u do ls vtec u have to modify a ls head gasket. the b series vtec ones arent compatible. i am also in agreement with what was said above....if ur gonna spin that motor past 7k u better upgrade the rod bolts. the pistons are just an added benifit because you get the greatest bump in compression. IMO b16 pistons are best to use with stock ls rods bc they press right on. there is no midifcation needed like type r pistons. so for example, using jdm b16 (p30) pistons with a gsr head and a 3 layer head gasket you get about 11.8:1 compression. thats about max for the street IMO. ur gonna need a fuel pump and bigger injectors as well. 200 whp is definately reachable n/a. like i said i was about 20 hp away with just a street tune and STOCk gsr cams. with bigger cams and a fuel system u can definately reach 200 whp n/a....especially at that compression level. good luck with the build!