I just picked up a 60 chev swb 2 wheel drive. It's got a straight 6, and three speed tranny w/ the hydrolic clutch. I'm wanting to install a car four speed, like a saginaw or muncie behind this engine. I was wondering with either of these trannies bolt to the bell housing and will I need to modify the hydrolic clutch system to work with these trannies? Or should I just install a turbo 350 auto? What tranny cross member will I need to make that happen and will the drive line need to be changed?  

I would install a 200 r4 or a 700 4r.  you will most likely have to fabricate a new trans crossmember and have a driveshaft shortened/lengthened accordingly.  I suspect that either manual trans would bolt to the bellhousing, but I don't know about the clutch question.  

Any 3 or 4 speed saginaw or muncie for GM will bolt into to your bell housing with no modification to the clutch system.  If you plan to swap to disc brakes in the future, I would suggest you go ahead with an auto tranny.  Your brake and clutch share a common master cylinder which is not adequate for disc brakes.  To swap to an auto, you will have to cut out your rear cross member where your standard bell housing bolts to, and build a rear crossmember.  Also as mention in previous post, shorten your drive shaft.