I put an industrial 350 engine in a 78 GMC 4x4. Had steel rods, 194 heads, windage tray and roller cam. Seemed to be a good choice as a replacement motor. Has headers, aluminum manifold and a stock roller cam. Block had cylinder wall damage which required it to be bored out .060". Problem is when the weather gets up in the 80s it overheats or when pulling a car hauler. I have a new radiator core which I bumped up from 2 to 3. I installed a high flow thermostat and put bigger jets in carter carb. It did help but not completely. I had installed an early dual plane manifold, flat top pistons and rebuilt engine with "95" engine gaskets. I did talk to a performance engine shop about problem. They felt the over bore was not the problem. Any ideas.