hi cracker jag diffs are 2.88 mostly autos 3.07 for 4 speed box 3.31 5 speed v8 3.54 ,here in uk 3.31 is the most popular with chevy 350 or 351 ford also rover 3500cc[ small buick ] ihave 351 cleveland zf box 3.31 diff 17in hallibrands , diff came out of xjs lots of rotten jags in uk .look at
www.ward-engineering.co.uk for crown wheel and other jag bits .i have a 1941 step side chevy pick up to restore after cobra finished cheers