340 runninng lean and overheating

My 1970 Swinger 340 did not have a overflow system. On trackday I was told to just insert the puke-hose into a popcan ziptied in place, and they would let me onto the track.This was a basic puke-tank system.

By 1973 it had morphed into a coolant recovery system, where the fluid gets sucked back into the rad as the coolant in the engine cools down. This is a smart deal, because the rad is always full, and therefore the engine is too ......... until you forget to check it one day. It's like having an elf under the hood, topping up your rad every night, until the well goes dry.

IDK about the intervening years.