To get more heat in the winter, for the engine coolant temperature or because it's cold inside the cab or both?
Adding a UV dye and using a UV lamp may help locate leaks. I've never tried it myself.
If you have closely inspected everything that was touched during the replacement and found no leaking, I would start thinking about things that may be affected by the increased temperature.
May not be the problem you have:
These engines, after many years, tend to collect rust in the coolant passages around #6 cylinder. If severe, it can cause that portion of the engine to overheat.
It happened to my cousin in a stock 50 Chevy. The car was a daily driver to and from work. He took it on a long vacation trip. It overheated.
The increased heat from the trip caused the rust to migrate. He flushed the radiator and the block several times. Luckily it finally cleared out.
The return home trip was normal.
Last edited by buoymaker; Sat Jul 03 2021 09:32 PM.