Your '85 Corvette motor would either have been rebuilt at least once (probably twice) to be in proper working condition unless it was a 'pretty' show car, which means it needs a rebuild now. At least half of the 'permanent' things around it would have been replaced; the alternator, the master cylinder for the brakes, any thing with the word 'pump' in it, probably the solenoid for the starter and the IM for the distributor (if not the whole thing for both). This is on top of normal, consumer-level maintenance (oil changes, brake replacement, etc.). The good news that we're dealing with Chevy parts, and that 2019 engine would be an improvement and likely more economical in the long run.