I need to determine the appropriate thickness for an FA16 flange for mounting an electric actuator capable of 740 ft-lbs of torque. I've measured cast flanges on Velan valves at 1.25". I've got a supplier who say's 1" is adequate when welded
I've established my preliminary standards based upon Manufacturer's Standardization Society of the  gate Valve and Fittings MSS SP-101-1989 and MSS SP-102-1989 documents. While providing critical info, there are no specifications for flange thickness.
The FA16 flange has a 6.5" BC using 3/4"-10 Grade 5 Bolts per MSS.
FEA is for finite element analysis. You probably don