The best way to measure the back spacing is with the wheel off. That said, I've done it with a tape measure through the spokes in the wheel. Measure the full rim width, then the front spacing (brake mounting face to front edge of rim). Subtract the two for the backspace. A piece of wood or ruler helps with getting the front space distance by placing the wood across the edges of the rim.
I have a new (never installed or used) Megasquirt MS230-C, this is a Megasquirt II ECU with PCB3.0. Firmware is v2.687. Also comes with 8' Megasquirt wiring harness and DB9 tuning cable. $400 for everything.
Interested in any New or Used GT40X or X2 heads (64cc) would consider other similar AFR's or Edelbrocks possibly.
Buy or possible Trade if you're looking for more compression.
Let me know whatcha got ! :)
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