20v head on a GZE bottom end, or using GZE pistons, would be fine, but yeah, stock 20v pistons are high compression. High compression + decent amount of boost = detonation. You could run a low amount of boost, but for the money you'd be better off doing NA mods like cams, porting, valves, etc. It's pretty much essential to have a low compression ratio for turbo applications, no more than 9:1. GZE pistons come in 8:1 and 8.9:1, depending which generation. You could always throw a very thick headgasket on a 20v to turbo it, or a decompression plate, but, you wouldn't have the strength of the GZE pistons, which from my impression, are quite well built. Mind you, I've always looked at the forced induction route so I have no idea on how 20v pistons hold up, I just know they're high compression and therefore unsuitable.
