1974 Plymouth Duster 5.2L

1974 Plymouth Duster318 V8 904 TransmissionRuns and drives but transmission is starting to slip. Motor runs pretty strong. It shifts from 1st to 2nd but won't shift over to 3rd because the linkage is not hooked up and I don't have the hardware to hook it up. It's had body work and a paint job several years ago I'm sure, but could use some better body work and new paint job. The lights are working, gauges are not working. It has a Sony CD player. Odometer reads 42 and some change, but I am assuming it's 142. Doesn't leak any fluids. Oil light comes on, but the oil level and pressure are fine. No knocks in the motor. I'm assuming there's an issue with the gauge. Cool old Mopar, would be worth restoring.