I had a 400 in a small motorhome and it had almost no heat for late season races. I was talking to my buddy that ran a local towing service, auto repair and told him I was going to try changing the thermostat. He recommended putting more clothes on and told me their issues. Never gave me one Ounce of problems.
A stock car friend built 377's. .030+ 400 with a 350 crank. TRW made the thick bearings to make it work. The damn thing sounded like no other car out on the track and ran like a scalded dog!