I've just recently put a CDTV-RAM-IDE - https://gitlab.com/MHeinrichs/CDTV-RAM-IDE - in my Rev 5 A500. It's a modest upgrade - no fancy features like acceleration or kickstart switching - but it's a lot cheaper. I really just wanted a 1.3 machine with HD and some fastram, something I never experienced back in the day as I went from a 1MB A500 with floppy drives to an A1200 and then A4000.
Unlike other cheap IDE devices that emulate the Gayle chip in an A600 or A1200, this one will auto-boot OS 1.3 with no other modifications.
You can see I had to lift it up a bit to get it over the kickstart chip.