well u can tell the rear end whether there is a pan on the back or not, if the rear has a pan on the back its a 7 1/4 if theres no pan and the thr3 member comes out the front its probably an 8 3/4 ,,, u can also go onto a website to tell the difference in the tranny pan to see whether its a 904 or 727.. or u could go on a site that has the vin decoder and that will help u also so have fun and good luck