Thanks for the replies.

I'm leaning toward the Veethree GPS Speedometer Sender 69248E. It's self-contained so I don't need to drill through the dash for a wire to an antenna. I think the integral antenna will do fine beneath the plastic dash top, based on what I've read about performance in classic hot rods.

I'm in touch with tech support for the speed control unit. I think any of these GPS pulse generators should work, because they are meant to mimic the pulse stream from a VSS and feed a digital speedometer, and that is the exact pulse stream the speed control is designed to be slaved to. I'm trying to work out the bare minimum electrical and vacuum connections so that I can "bench test" the speed servo with it sitting on the seat of a car. Then I can return and order different GPS senders as needed.

I'd love to find a handheld or mounted nav unit that would provide the pulse stream, but I don't think it's out there. At least not for $100, like these dedicated GPS pulse generators.

Thanks.

Steve