I was searching out a SCA to 50 pin adapter and found this on Amazon: https://www.amazon.com/CERRXIAN-Female-Adapter-Converter-Computer/dp/B09G27DNN4/
It claims to be a SCA to IDE adapter using a 50 pin header. I'm sure it's a typo but... was there a 50 pin IDE standard?
I've been puttering around with my Powermac 7100/66 and while they're a steadfast beast, it's a bit on the slow side.
After finding a couple of PDS-mounted processor upgrades on eBay, I've kinda noticed that you can find the processor upgrade cards but never the chassis and flat flex cabling...