TKX into 72 Duster issues

Good evening,
We're putting a Tremec TKX 5spd into my '72 Duster 4spd. I have Autometer American Muscle Gauges. We can't find a part to convert from the TKX speedo to the electric gauges. I called SilverSport, they recommended Autometer sensor part# 5292. It's way too big and there's not enough meat to cut-to-fit on the car or sensor. I don't want to go GPS speedo. Any other options? Who has done this swap with aftermarket gauges? Thanks!

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