Hope this helps... on my 70 parts car,both outer front mounts were bolts, the rest were studs...make sure that the spacing on your seat tracks are roughly 15 inches give or take front to back...I know other gm cars had a shorter distance roughly 12 inches....My 72 Custom has a different stud/ bolt hole arrangement than the 70. I'm not too sure about the 71's...What i did on my first 72 which was a bench car,used the original outer mounts and drilled where it should sit and bolted right through into nuts with washers....I didnt get any pics of that though..... Anyone else that can chime in to help?