Just installed my supercharged proficiency engine, don't need this anymore. If anyone needs a late gen 1 (delrin QD bolt, not the attached bolt or the original metal QD bolt). It's in FANTASTIC shape, only had maybe 10-15 cases through it. $25 shipped to your door via USPS Priority.
Oddly enough, this is sold. Who'd a thunk someone would actually need a stock engine for a Marq with the proficiency and supercharged proficiency engines out there?