Regarding differences between Thriftmaster 235 and Loadmaster 235:
The Loadmaster had:
1. exhaust valve rotators
2. exhaust valves were made of XCR alloy
As Mike posted above, these minor "internal" differences resulted in no higher power (but, perhaps a longer-wearing Loadmaster head?).
There was about a 10% performance increase in 1955-2nd 235s compared to 1955-1st 235s (beside the difference in the water pump locations in/on the blocks). And, there was a 1st-2nd difference in the valve cover, if the engines did not have the PCV set up.
