are they 4x4 or 2x?

I prefer the 85 wire harness over the 89

the c-body 727 and 440 fit right in either of them if 2x chassis

440 fits either if 4x4 but need the 727 4x4 and xfer IIRC 85 & 89 4x4 are same xfer

if manual 4 speed the 89 will be hydro clutch

axle spindles chassis body wise the same

440 RC either 2x or 4x4 is cool and do-able