I have a 3.08 limited slip rear end in my 89 TA 5 spd 305 with headers. I wasnt to go faster but I dont want to lose top end speed. I was thinking about getting posi and leaving it a 3.08. I dont have a lot to spend so getting gears is too much. I was wondering if a rear end out of a iroc or gta might have a 3.42 posi and be cheaper. Also if I do change my gears how much top end speed will I lose, and how much will my spedo. be off?

Kris