Seems there is a difference between the coolant capacity (2+ gallons worth!) of some of the 94-96 and the 97 PSD....how do you verify this difference without draining all the coolant to measure?

I have the manual for the 97 and it calls for 33.75qts, the 96 manual: 22qts....

Reason for the Q: I had a 97 PSD that never had temp needle climb on hard pulls up grades, but my 96 seems to get way up there whenever I push it hard when heavy (10k+) up the 6%+ grades. Thermostat is good, clutch fan works, (but doesn't seem to stay engaged past about 2000 rpm...then roars back on below that rpm), no crap in the radiator fins or between it & AC. Belt in good shape. Clean anti-freeze, been regularly flushed...

Any easy way to know how much my 96 holds so I can get a 97 radiator if needed? I need more cooling ability...

Thanks for any help or advice!
Erikk....