Nice! If your dad put 4.10 gears in it (not available from factory that year), he may have also put a shift kit in the transmission. That would explain why it shifts “rough”. I’d suggest you do basic tuneup (spark plugs, plug wires, distributor cap & rotor, fuel filter, change oil), clean it up and drive it. Enjoy it before you start tearing it apart. You’d be surprised how many cars sit in the garage for years, because owners got in over their heads. This forum will give you all the help you need. Welcome!