I did this exact change in my 1965 Short-box fleetside. Just bolted in the frame bracket from the 292 equipped truck (the holes were already there) and used the original 3 speed bellhousing but installed a S-10 5 speed trans in it and used a driveshaft from a 1955 Chev car....fit right in. Now have an HEI in it along with an Offenhauser cover and intake, a Holley style carb from Tom Langdon and a set of Dyno-Max coated headers..fit real nice. Just trying to get it repainted right now and run it for the summer and then maybe we will contact you Lee about some ideas for the motor. Everyday driver so don't want to go stupid on it, maybe a little head work and a mild cam. You will definetly like this etup in your pickup. Good Luck
