Sounds like you need to address your stock cooling system, clean out radiator, clean rust out of block, make sure t'stat is functional, can use 4# radiator cap, install overflow tank- Dodge has some vertical ones that fit old trucks well, make sure engine timing is correct. Back flush radiator with garden hose to get bugs and seeds out. Can use cab heater when necessary. Puller fans are more efficient.

Good luck.

Ed

'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.