As many cars that have gotten V8’s swapped in there should be a few around to get you bolted together.. The engine mounts are probably not unique to the Nova.. The frame stands probably are Nova specific. I know I have another front clip with six cylinder mounts in it..
The trucks (or some trucks) use a different mounting system and I think the 292s are different. But yes, pretty sure Chevelle and Full Size are the same. Some of the L6 stuff is starting to get scarce as everyone throws it away. This is one of those items that gets ditched with the block.
There is a small, but healthy market for L6 parts. Truck and boat enthusiasts buy stuff and of course the random Nova owner. I usually have no problems selling fairly priced L6 stuff on eBay.