I have seen new cars in the factory melt carpets because of a lean condition and the repairman left the car running to warm it up when he went on a coffee break. cars with the thermactor or air pump system ran extra rich then the air injected into the exhaust continued the burn process. try to fing a good set of Ford 460 passenger car headers, most are burned and cracked. it never made sense to me to burn more fuel for emmision testing but the rules were to read so many parts per million. a lot of fuel burned but at the proper mixture to get a tail pipe reading to pass not how much total polution is produced . some smog tests tech.s. end up adjusting the idle higher to get out of the idle rich circuit to get a car to pass.
A lot of GM starters don't like heat.. if you have a GM Starter, (some were used on Fords, 429 and 460's) you should use the ford fender mounted remote starter relay. most magazines have shown how to do this, also you probably need spark plug wire heat shields with headers,