is there any way to convert my 91 trans. to work with the cable driven speedometer in my 89 camaro ------------------

Yes. Two ways.

First, you can get an aftermarket speedometer that would run off of the new sender.

Second, although I've heard it and never done it, you can take the whole speedo gear set from the cable set up and put it into the new tranny (assuming it's a 700-R4) and then hook up as normal.

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'84 Trans Am
Crate 350 - 4 bolt main, Holley 600 w/vac. secondaries now open element
T-5 - Stock with Zoom clutch and PP