The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Any advice from rebuilders out there?

Has it been sitting a long time? Maybe carb issues. Valve problems will cause some if not all of the symptoms you describe. For starters get those valve covers off and see whats going on there. What transmission does it have? Three on the tree or floor shifter? If its floor, you're goin' nowhere fast in 1st. Thats for starting out with a heavy load or pullin' tree stumps.
A small block is not a ridiculous idea. In fact, you'll probably see more V-8s than anything else in them nowdays. Most dont seem to want the original engines.
Oh yeah, welcome to the 'Bolt. Others with much more knowledge than me around here. Be patient and you should get some more responses.
Jeff