My Thordarson catalog did not have a competitive cross, but if it is any help, the 76 driving 2-42's is rather a common setup. It is also about the same as the transformer between a 6sq7 or 6C5/6J5 and 6F6's, so if nothing else, if you have a parts chassis for a radio with that set-up, you have something to fall back to.
If the physical size is about correct, assuming there is not a good winding to use for at least a partial compairison, your could try it. Just keep an eye on your 42's plate voltage, as well as the plate voltage of the 76 when you try it initially. Tubes are more robust than solid state, but not totally immune from harm. Get your voltage measurements within 45 seconds of unit being turned on. You might even want to just clip the leads on from the start so you can see your voltages from turn on.
: Hello I have a bad coupling transformer that couples the 76 Driver to a push - pull pair of 42's. I need to know if someone has an old Hammond catalogue and copuld look this up for me as I have access to a 332 coil. I have also been told that a few other numbers in the 3's and 4's might work. If there would be a better number to use or if the one I have would work I'd like to know. The radio is a GE M-81 equal to an RCA 143 and 242.. I have the schem if this would help. Thanx Brian