I saw the photos -- but it was not clear from the photos that all the SCRs were the same part number -- just the same family of parts. It could easily be that half of them are grounded cathode and half grounded anode parts. The part numbers were not visible in the photos. :-)
The test would be whether one wire of each pair feeding a gate is shorted to the stud in *every* SCR. If not, then some are likely grounded anode -- and that would actually make sense to make a bridge rectifier. I would expect the black wire to be the one connected to the cathode, but I'm not sure.
And -- are the studs electrically connected to the heat sink, or are they insulated? Such rectifiers have long been sold with mounting hardware which consists of a pair of large diameter mica washers, a Teflon ring washer to hold the stud centered out of contact with the metal of the heat sink, a flat washer and a nut. Also -- they normally are mounted with a heat sink compound (with or without the insulating washers) to maximize the conduction of heat to the heat sink. Anyway -- if they are mounted with the insulating washers, there will be ring terminals connecting to the studs to complete the circuit.
It really would have helped if you had not stripped it apart. it would work a *lot* better with the original driver board.
Can you still identify the driver board that all those gate connections were connected to?
Don't get rid of them until you are *sure* that you don't need them. You will probably need quite a few of them for this -- and having spares helps too.
I just recently got fifty such relays for future projects.
Good Luck, DoN.