Thanks Bill, I somehow knew you might have the answer

I completely removed the '88 computer system so I have to feed the speedo from the transfercase.
The T case is a 241-C and should produce 40 pulses per rotation
I kind of want to keep the look of the stock YJ dash. Is the TJ speedo 3.5 round, i can't remember?
I might just have to use a handheld GPS for a speedo.