Taylor,
That OERM turntable is the third "new" turntable built in the past decade.
Standard Gauge, w/ 3' gauge guard rails:
Nevada State Railroad Museum
Folsom (California) Railroad Museum
3' Narrow Gauge:
Orange Empire Railroad Museum
All three turntables were built with the same castings to similar design. The Folsom RR Museum website has pictures of their turntable underconstruction.
The OERM table is based on the 56' SPNG table at Laws, Ca. The biggest thing, that I know of, that was ever on that table was SPNG 2-8-0 #1 which came in around 94,000lbs (47tons).
Tracking down the old SVRy steel table and either fixing it or making a replica would be money better spent.
Just remeber, mikados & Heislers were designed to go forward and backward. If SVRy plans to run engines without trailing trucks (2-6-0s, 2-8-0, 4-4-0s, 4-6-0s) they'll want/need a table at either end of the track (or a wye).
Cheers,
Curtis