I am new to forum and have a problem. I have a 4 bolt main 350 from a 1974 corvette in my street rod. Rod is a 1940 Ford 4 door pickup i built on a truck frame.When first built there was no problem with heating. I have heating problems in the last 5 years that have gotten worse. When i check temp of exhaust header tubes, #3 and #6 are 100 degrees hotter than the rest of the tubes. 400 degrees or more. I have had radiator flushed. It was OK. Engine flushed, OK. Checked water pump, also OK. Last year i removed heads suspecting wrong head gaskets, and found 400 head gaskets on engine, no center water passage holes in gaskets. Replaced with correct gaskets and still #3 & #6 hotter. It is has Edlebrock cam & lifters and carb. Put new Accel Distributor on this summer. I think if i can fix the problem with #3 & #6 exhaust i might fix overheating problem. Any suggestions would be appreciated.