If I were you,and wanted a reliable daily driver,I'd order the catalog from Patrick's Antique Cars and Trucks. They specialize in "our" 235,and 261's. They also have a section for our G.M.C. "brothers",covering complete rebuilding kits for the 270,and the 302. They also carry transmission and rear-end kits,for CHEAPER than you could buy an S-10 for. This way,you only need to invest in one vehicle,and not worry what to do when the neighbors complain about having a truck in pieces sitting next door. And the tranny is designed to bolt right up to your stock "six"! Several Great vendors though! I've dealt with Jim Carter,Patrick's,L.M.C. to name a few, as well as several fellow "Bolters"that I've bought parts from. For performance and reliability,I'd go stock. To save a buck,I'd go stock..as well as headaches of not figuring on something,when patching two trucks together. (wow-that don't fit too good). Been there, done that. I'm sticking to stock, myself. I'm gettin' older. "Take the path of least resistance" Good-luck,no matter which way you decide to go.B.T.W.,I've got 6500 dollars in mine right now,and its a '55 2nd 6500! Yeah,2-ton! It's not near done yet. It needs more body-work,but I painted it anyway just to keep it from rusting. I probably wouldn't get 1/2 of that for "her today,BUT then again,I wouldn't sell "her for less than $12,000! Yep! NOT For Sale! The more you work on them,the more you love 'em! "Keep on Truckin'"!
I paid $100 for my S-10 frame, already stripped, and had another truck for parts for $100. If you can buy a motor and transmission kit for $200, you better go with it.