Jeff, I almost bought a fairly nice redone TR4 a couple of years ago, we were talking in the $3500+ range, new top/interior/tires, webers, minilite mags, fresh paint...in researching it, there's a bunch of Triumph maniacs out there (like us!) and the price of good restored examples could go for $7000+. The cars are an absolute hoot, and will keep you off the street fixing
oil leaks and other (Lucas) items. For the condition you describe, maybe $750 if he wants to let it go, $1000 if you want it badder than he does, depending on whether the top and interior are still useable. Could be a painless resto or a nightmare, but if it is in AZ I'd bet on a piece of cake. Lots of parts availability on them too.
Who nose, maybe the tranny problem is 'cause the clutch is out of adjustment?