Unfortunately, there were 3 new boilers built by the Texas State Parks department for the TSRR locomotives, rather than simply rebuild the old ones. The first was built for TSRR #300 (now T&G #28) and basically duplicated the old Baldwin 1917 boiler.
Then someone got creative, and no one at the RR or in the State Parks adminstration had the knowlege to question, or even asked anyone with knowlege. The boiler for 316 was built to much heavier standards than the original and then the one for the 1316 made even heavier. Both were basically built like power plant boilers as Earl states, and in that service would have worked.
Unfortunately, I have never heard that the State never consulted a railroad boiler expert before having the boilers built, and neither Earl nor Steven Butler were anywere near the RR at that time.