Doh! My suspicion that the throttle cable was crossed/wrapped on the clutch cable was correct. Fixed that and then re-adjusted the cable tension at the trans bellcrank, and we're good to go. The car actually returns to idle now, what a concept.

Supposed to go on a local canyon run with Jack Olsen and a few other Pelican 9-eleben guys in the a.m. tomorrow. I will try to remember my camera. Unfortunately I haven't gotten around to wiring up the in-car video yet. Maybe I'll get ambitious and try that later today.