Lots of issues here. Biggest factor on engine time is usage. A 400 hr engine OH 20 years ago is about as good as an 1800 hr engine oh'd 7 years ago. All Comanches are pretty much the same airframe, and many have been modded to the point that model year is almost irrelevent. The biggest item is the early airplanes didn't have the aux tanks so the 250 range was a bit limited with the 60gal tanks. This is remedied very easily with those airplane with tiptanks having the same capacity as those post '62 aircraft with factory aux tanks. I own a '59 180, don't need or miss toe brakes (cant turn any tighter with them, than without, and they actually cause unecessary stress to the gear legs) and have modified it with all the speed mods as well as new panel and interior. It always fools those not in the know. They think it is a recent build airplane. Model year on Comanches is a blurred subject as it means very little these days. A late model can be unimproved where an early model may be highly modified to the point of a new airplane. I know which one I'd want! In 1972 the primary accounting aid was still Burroughs adding machines....and I wasn't born yet...sorry
-Zach