4-doors almost all cost more, but the condition of the tops and doors is almost universally junk. Look at the price history in your area...if 4-door units are going for $2000 or more, just buy a better-condition 2 door unit and buy a BRAND NEW 4-door kit from Breton (they make the official US Gov't Issue soft tops) for something like $2000 delivered, all doors, all hardware, all brand-new. I'd like to recommend buying something private sale to anyone even a little bit feighnt of heart on the matter. Private sale prices have finally come down out of space and it looks like you can get one in running condition, ready to drive away for as low as $10,000. With an auction that might close for $6-7k, you have to wire your money within 3 days, fill out a chunk of paperwork, wait 1-2 months, arrange a transporter or prepare yourself to transport, break your schedule to go pick up your HMMWV on the only day or two of the week they'll allow a pick-up in an 8-day window...and only THEN do you start working on the HMMWV to get it up to operating condition, which could be a couple hundred dollars or several thousand dollars. Oh, and the dance of paperwork once you get it home to attempt to actually put the vehicle to use as a farm truck or an OHV... It's a lot of work with a lot of risk. Private sale cuts a lot of that out.
EDIT: Spelling. It's Breton, not Brenton...
