I did them all studs. found studs that were threaded all the way down with no middle section that did not have threads. the ones I used had a philips head cut in the top and I put them in with locktight...red I think. then just went back with gasket/windage tray/gasket/block. used nuts and lock washers. It went fine. some of the holes with be different depths on the block and it will looks like the studs are all different lengths after you put them in....kinda like a third grader measured them, but worked fine. I think in the 2 or 3 front ones where it goes through the cover (nonblock), I just used bolts. I found out some of my bolts had bottomed out and was leaving me persistant
oil leaks because I had not tightened the pan up to the block well. I kept retightening the bolts, and still had leaks. Did the studs and now I know I have a seal on the pan, and no leaks again...worked great
Buzz