If i wanted to get higher compression piston for my 98 ls do i neeed to buy new rod or the stock one is fine???...and if i buy like 10:1:0 or 11 would it be bad for the engine or is it fine???...

buy ctr piston.there cheap but you have to modify your connecting rod.your rod will be enough strong.

Just curious why you're doing that. It should be fine as long as you run supreme, its 91 around here, but Ive gotten some at 92 before.