Just one thought on your overheating. First is it overheating in traffic or when you are driving down the road? I have a 69 Swinger 340 and no matter WHAT I tried I just couldn't get it to run cool in traffic. After trying every cooling trick in the book I stumbled on the cause. If you have a fiberglass six pack hood like mine and it does not have a rubber seal (like the factory hoods) on the underside of the hood that mates with the rad support, hot under hood air will come out from under the hood and will be sucked back through the rad and will be heated up more and then back out and back through the rad and eventually the car will overheat. I temporarily used foam pipe insulation held onto the rad support with zip ties. What a drastic improvement. Give it a try it's a cheap test. Good Luck