The part number for the Fel-Pro 2-piece rear main is: BS40613 (this came from a post in the TTA tech section, and I assume it's the same as the TRs). I used the side seal installation pins on mine plus GM anaerobic sealant on the main cap face and in the corners of the saddle about 1/4 of an inch on each side where the side seals bottom out. Most will say not to use the side seal pins, but it worked for me. Others will say use RTV instead of anaerobic sealant, but an anaerobic (unlike RTV) cures in the absense air. I'll bet most won't use an anaerobic sealant because of price ($18-25 for a 2 ounce tube, or $6 for 2/10 of an ounce from GM). IMHO if GM recommends it, that is good enough for me.