Yea thanks for the tip!
I believe I posted this in another thread, but lowering the timings from CL3 to CL2 gave me another slight boost. I got 3 PC133 sticks today and they all worked fine!
I am confident now that once my 1.4 GHz S370 cpu arrives I will have reached the (for my project) perfect 386 speed (386DX 25 MHz) with room to slow it down as needed through the BIOS (FSB and RAM speed).
Yes there are plenty of S370 boards with ISA. You can go even faster with early socket A boards, that is something I will surely look into.
Another option are these industrial boards, though very expensive at several hundred dollars. If the BIOS in those boards allow lowering the multiplier, then using any current Celeron like a E3300 would allow you to do some amazing things.
You could not only lower the CPU speed from 3 GHz down to 800 MHz, you can also lower the Ram speed and therefore have a massive performance scaling from top to bottom.
So yea, lots and lots of options. However S370 is very cheap. Boards are much easier to find and cost less and 386 or 486 hardware. They are ATX so can use new cases and power supplies, they work with current IDE DVD burners, documentation is readily available, no jumpers because you set everything in BIOS or it's set automatically....