Well the difference between T1 and Peppercorn et al is that it seems the English folks have ponied up a LOT of money to restore dozens, hundreds? scores anyway,
of hulks that for the most part sat at Barry for many years.
Now some of the "replica" works are utilizing the last parts from Barry,
because BR standardized as many parts as possible, including boilers
Most are to replicate a class of locomotive that didn't go to Barry [ only locos in service in the SW of England went to Barry, others went to the nearest scrapyards] so none survived.
ONe replica well underway is a 2 ft gage 2-4-2T that was built by BLW for Lynton & Barnstaple.
NOw it seems to me that the English have it "easy". because the typical engine bed is a "plate frame" all you gotta do, once you railse a few million pounds, is cut plates to shape and rivet them together into a box-like thing.
T! and anyone else who attempts a modern-ish US loco requires cast engine beds.
Making a pattern and casting a driver center from the appropriate alloy is impressive, but an engine bed ??
Does the capability even exist in the US or anywhere in the world??
Waaay back in the 80's there was talk- reported in PAcific News- that perhaps a replica SP 4-8-2 could be purchased from China, which was still building steam'
If only I hadn't squandered all my income on food and shelter

Oh and one last thing, NEVER put a dash in ANY PRR class. The smallest dash is like an atomic wedgie to those folks