When this was released I fixed a few dead boards I had tossing around here.
I'd been using them for parts for years and tossing them like a Frisbee from place to place because they were pieces of sh!t

So then I had to find all of them and find the spare parts I pulled off and put them all back together again.
I've done a few carts here so I could offer the switcheroo service too.
The CPU's I used came from dead STV boards that mostly had damaged cart slots and other unfixable issues.
I never had any issues they just worked first time hehe! but of course I have about $50k in equipment and my technique is honed over 20 years of working with electronics

The biggest problem with CPS3 is the speed. The SCSI works only at PIO speeds so that is why it's so damn slow.
I suppose I could do a tutorial, but it's not that difficult. Just swap CPU and TSOP48 BIOS, or in the case of the factory CPU, just swap the TSOP48 BIOS. Then use the Darksoft CD. I did the work some time ago but from memory that's all there is to it.