Updates, folks!
I printed out a picture of the Autometer sending unit and took it to the mechanic; he said the one that's leaking looks like it, so I'm going to order it from Summit and bring it in. I really miss having a driveway to do this stuff in....
Anyhow, in the coming weeks, I'll also be installing an Accusump I acquired through Swazo (proud to have some of his car in mine!). Could I safely split the tap the sending unit is using to input the Accusump? I'm only asking now, as I'll order the fittings and all at the same time.