tinstafl and others
Trust me ...there are no augmenters on C or later models. Of course, the big differences on the C and later models were the use of the IO 540 C4B5 engine which is fuel injected with light weight props and alternators and the 400# increase in gross weight to 5200#: A/B models are carbureted with generators and old style props.
As between C an D strictly cosmetic and mostly on panel and larger rear baggage space/door. E/F models had pointier nose ...better radar capability.. and changes in horizontal stabilator plus some panel layout improvements.
If you are looking for long range suggest one with METCO tips and Miller nacelle tanks for 230gal usable fuel or 10 hours @60% and 165k.
With respect to hydraulics the best way to go is the aux ELECTRIC hydraulic pump mod ...had one ,worked fine. The comment about the wheels sticking out a few inches in the retracted position is true only on the A/B models. C and later have gear doors ....but once you shed these fiberglass fairings on a gear-up the wheels will support the aircraft a few inches above the surface..moral, land on a hard paved surface, flaps up:
props are goners unless you are brave and expert enough to kill engines on short final, feather and use starters to get blades horizontal...it's been done with only damage to gear doors and belly mounted antennas/beacons.
High maintenance items include engine mounts and exhaust systems. Old style oil coolers subject to problems due to vibration.
Hydraulic pack has limited life.
There's more...but still a great aircraft....I'll get back to you.
xaztrucker