75 G10 shorty van with 12bolt rear?

Hi there

Any advice on where to purchase a taller ratio ring and pinion for above mentioned setup?
Something like 2,70 or 3,0: 1?
Or do I have to convert to a 9" Ford setup to get that tall a ratio?

Thanks in advance
Borcher

Welcome!!! Check vannin.com for better knowledge on 3 rd gen chevys