Hey guy's so i bought a truck off this kid, (dumb i know) but i got a good price, I'm a cummins guy and not to familiar with the chevy T cases. I know theres 3 different spline types for 1/2 ton 3/4 and one ton? The kid ripped the tag off and the only number on this thing is the casting number on the rear housing. I have 31 splines so is mine the 261hd or 263hd? Any help would be great i just wanna make sure i order the right parts. I also have the inch and a half chains, thanks guys, Greg 2004 GMC 2500HD LB7 DURAMAX ALISON TRANSMISSION.