Wear and tear?

[Roger Mounsey]

Hi. Finally got my car on the road, and after 50 miles of driving and
noting a grumbling from below and leakage from rear of center diff onto
exhaust took the 4kcsQ to a Q-list recommended shop for evaluation and
inspection. He says that my car had its odo rolled back, that the
powertrain is worn out and that the car has more like 263k miles than
63. He said that the engine was tired (without even taking a compression
test). My own experience was that this car, outside of the trans/center
diff,drove rings around my relative's '95 Integra w/87k mi - it has no
clunks, squeeks, rattles, brakes w/apparently original lines feel great,
seemingly original rear springs don't sag, engine runs without much
noise/smoke (can barely be heard @ 50-55 mph), has a slightly floaty
feel on the highway compared to a 325  ("softer" car) but basically
drives, looks, smells,  and feels new - even the front seats, pedal
rubbers, shift boot, etc. Opinions?
By the way, I now needa temporary Beater 4kQ as long as its mechanically
good, will pass inspection, and has a trans/center diff good for about
100k mi and the rest of the car for at least 25k mi. Don't care about
appearance, but need for work pretty quickly. 
Regards, Roger.