I don't have any 6 or 12 MHz crystals but I have active crystal packages (containing the active components to oscillate when power is applied). I also don't have the 22 pF capacitors to go on both sides of the crystal. So I will have to order crystals and capacitors for production, they are cheap enough.

In the event, it was good that I used an active oscillator, because I added a binary divider IC (74LS74) so that I could use 6 and 3 MHz clocks to check my MCUs.

All of my MCUs work at 6 MHz. Some can be clocked to 12 MHz.

There was one that didn't blink the LED when powered up. Then I noticed the power supply voltage was drooping. I touched the chip. Ouch! It must have been molten silicon inside and soon the smoke inside would have escaped. The chip was not labelled 8042 or any of the other numbers, just read Fastest BIOS chip. So it could have been another chip, maybe an 8051, or even a bespoke chip just for that motherboard. After all the interface to the x86 CPU has only to be at the register level, and the interface to the keyboard at the serial line level. I probably killed this chip, but never mind, I don't know what it might be and will never know. Anyway heads up, check that your chip is from the 8042 family if you don't want to let the smoke out of the chip.