I have a 77 250 with a 400. It has the stock mani's on it and i want some heddman headers. I live in PA and its about 30 degrees out. Please give me the best way to get them out with out snappin a bolt. Should i warm the engine up for a few mins?? Spray PB blaster?? I don't want to heat it up too much and then they snap, but don't want them to snap from it bein so cold out. It needs all new exhaust and I want to go ahead and replace it all since i have the time and money to do it all.