I need a taller rear axle ratio in my '87 190-16 Cosworth. Will diffs from other 190's and 300e's fit and what ratio would give me around 2500 rpm at 75mph? I am now buzzing along 3500 at 75. There are plenty of used diffs out there but will they bolt up? Anyone know the ratio in these 190-16'? I need to do the masking take mark on the driveshaft and count the number of times it rotates per wheel revolution. Help! George