Awesome info @hohum! I'm going to be using the wraith cooler off the 3700X as its what i have spare. My board is a 1.05 and was going to use some Corsair 3500LL (the modules with the cool activity lights on). I'd keep the board. They don't come up on the bay very often!
Think you may be good then, but perhaps give it a couple of runs on memtest before installing an O/S to be sure! Doesn't work on mine, but I have a 1.04.
I came across a similar one last night - an ASRock something something 939 Upgrade. It only had PCI-E but had a slot (like Slot 1 kinda slot) for an AM2 CPU. Not sure how you were meant to cool it... Interested to see what you do with it!
Yeah, they released a number of boards with this slot, but I don't recall ever seeing a upgrade board for sale anywhere! Must have had very limited availability. This link covers it, although as you'll see from the images you're pretty much limited to using the stock AMD cooler only due to orientation/clearance issues: https://www.ocinside.de/review/mainboard_asrock_939sli32_esata2/4/