parts needed during my recent transfer case (t-case) replacement, these are the parts the 88 service manual listed as non-reusable:

part number: MD739566
what is it: adapter gasket (between transmission and transfer case -- disassembly step 12 on page 21-14 in 88 service manual), this one felt like some kind of metal, maybe aluminum, as opposed to the old one which felt like paper
vehicle: 88 4-cyl 2.6L manual transmission Montero
price: $2.55 from Mitsu dealer

part number: MD716587
what is it: control housing gasket (between transfer case and gear shift assembly -- removal step 14 on page 21-43 in 88 service manual)
vehicle: 88 4-cyl 2.6L manual transmission Montero
price: $2.10 from Mitsu dealer

part number: MD704159
what is it: housing cover gasket (between gear shift control housing and housing cover for the t-case shift lever -- removal step 12 on page 21-43 in 88 sevice manual)
vehicle: 88 4-cyl 2.6L manual transmission Montero
price: $0.72 from Mitsu dealer

part number: MD704190, two of these needed
what is it: control lever gasket (one is between transmission control lever and stopper plate, other is between stopper plate and control housing -- removal steps 6 & 8 on page 21-43 in 88 sevice manual)
vehicle: 88 4-cyl 2.6L manual transmission Montero
price: $0.90 each from Mitsu dealer

special note: MD701722 which is the part number for the spring pin (roll pin) used to attach the transmission change shifter to the transmission gear shift control shaft, turned out to be too small in diameter to replace the spring pin I took out, so I reused the old spring pin (disassembly step 7 on page 21-14 in 88 service manual) ... it was only $0.73 from the Mitsu dealer, so I didn't bother returning it

had an '88 Montero, then an '04 Rubicon ... sold 'em tho