I'm mostly using this thread as a place to track this car, so I found this looking up my issue and quoting it here:
Originally Posted by Ninety5Aero
Update! Got the starter out of the car, discover it's already a Bosch factory rebuilt and looks brand new. Jerry rigged it to the very same battery, and it spun right over- no hesitation at all. So, I start looking at bad or loose grounds. Sure enough, the damn ground on the tranny was loose as a goose. Tighten it up, put the starter back in, the car fires right up! Son of a bitch!