hello I have a 91 f-150 i put a motor out of a 1994 full size bronco (302) I had to pull the heads to have two bolts machined out that broke off when I removed the intake (as always of 302 efi) replaced with new fel pro gaskets and new intake gaskets it run great for about two months and now I am overheating I have put in three thermostats and a aftermarket water temp gauge to make sure of actual water temp it warms up normaly till about 160 and then it skyrockets and will peg the gauge out before it stops if you rev it up a little it will start to cool down a little but don't I am not finding any water in the oil and no oil in the water it was surging through the heater core and i switched the heater hoses and that fixed that problem i have no idea what is going on so please help thanks