Last winter I changed the thermostat from 165 to 180. And also put on one of those safety caps. Ever since I have had an issue of antifreeze smell after driving a while. Drove it yesterday and today and the same thing. I have a leak somewhere because is residue on the alternator. It is a 1954 with the straight-six. It did not overheat. I check the housing bolts and they are tight.
If there is no overflow tank, not standard, if filled to the top when cold, there will always be some water overflow as the engine heats up. Filling the radiator to an inch or so below full will stop that problem, a non-standard overflow catch container will also solve that problem.
I also replaced my 160 with a 180 (which tested out to almost 190!), and ended up springing a leak in my heater core. I switched back to the 160 and replaced the core. Hopefully you don’t have that problem.
54 Chevy truck specs:
A stock radiator cap pressure valve opens between 3-1/2 to 4-1/2 lbs.
A stock thermostat @ 29 Hg Barometric Pressure opens at 148 to 156 degrees F and fully open by 176 degrees F.
I wouldn't go higher than a 4 lb. cap for risk of damaging an original radiator and heater core.
From the radiator fill neck, the overflow tube runs down the side of the radiator (passenger side) to let the coolant hit the road.
If your alternator is on the driver's side of the engine, I would look around the water pump and thermostat housing for evidence of leaking.
The truck has an aftermarket aluminum radiator. I have driven to KC 9 times over the last 11 years in Sept 95 degree temps running 70 MPH. with no issues. It has an aluminum overflow tank on the firewall. It also has an electric fan but I rarely use it. Before I replaced the thermostat it would not run as hot as it is now. Soon it will be my daily driver until decide what I am going to do about a new car, I am giving my granddaughter my 2017 Encore in about a month. One problem is I have one of those safety caps with a release lever and it does not always seat the lever in its slot. I just put it on new. I may go back to the 160 thermostats.
What pressure is the cap you're using? Maybe go back to the old cap and see if the problem goes away.
Sounds to me like the cap may be suspect and would be the first thing I would replace. I have a ‘59 235 and I put a 4 lb. cap on a stock radiator with a 180° thermostat. It runs at 180° constantly.
I did some sleuthing and found the old cap and thermostat. The thermostat was a high flow 180 for off-road use. I have ordered a new cap that is a lower pressure cap. Today's temps are to be in the upper 70s so it might not be the best time to do a test but I will anyway.