the gcco661- then on the center section it has b812 the reason is that when i get ready to order the power trax for the trear end they wanted to know 8.2 or 8.5 so thats the confusion,as far as holding up i am aware that its not the best way to get it done but i will run it until ir wont ,here in lawton oklahoma those rearends are platinum cant find ,and im not shure of what to retrofit it with you may see the video of this car and it does have the rearend being shown on streetfire.net then videos then type in old school chevelle that is my car i appreciate all the help honestly i have not found anyone around here who can tell me what the rear is as far as 8.2 8.5 please take a look at the video sound is on media player so if ya dont hear it top left click above pic thanks for the support this is my first time to use this web site kinda good to have the help thanks bryan........