Got a 69 Nova with a 4 speed. Unit pulls good in 1,2 then going into 3 starts to have what feels like a little slippage. What needs looked at? Clutch/pressure plate? Tires are factory size.rear gear stock.

Get car rolling about 20 moh or so, shift to 4th and floor it if clutch is slipping you will know it. If slipping you may just needTo adjust it some times the wear will have travel limited and not allow full engagement. If thats not issue you need new clutch and pressure plate and maybe flywheel surfaced. Flywheel may not need anything I have swapped a bunch of clutches and never touched flywheel.