Well, I opened it up today and it took about 3 seconds of comparing them in real life to be like "Oh, wait, no, that's not gonna work." It's a similar hole layout, but different positioning. With a fair bit of modding it might be possible to make it happen, but my willingness to use the dremel was basically "I might add one hole to the cooler" not "Well I need like 5 holes and some clearance and etc."
On the plus side, put on some thermal compound (arctic silver M-4) on cause I that thermal pad ripped anyway (all the rest were fine, just the GPU itself) and added those 4 washers aaand. . .well, it boots anyway, so I'm thinking I didn't break it.
Looks like I didn't get a noteworthy improvement tho, either cause my thermal pad was a bit better than average, or cause I did a bit worse than average putting on the compound, maybe my washer are too thin, come to think, there could be a lot of reasons I didn't get an improvement on temps. But, actually playing RDR2 for like 15 minutes, tops out at 85c and it's always leveled off around there. But, three hours on this was fun, if pointless. Chasing down a real improvement from here would be time-consuming, frustrating, and also pointless :P.