Can I replace my 383 rear main seal with motor still in the car?

other things to check=oil pan gasket loose from the bolts pulling the holes up towards block and not letting the gasket seal. the space between the rear main seal cap and the block has no rtv in it. the side seals are leaking. oil dripping sown from the valve cover gasket running down the block and along pan rail to back of motor on to the trans. pan gasket srunk from all the heat cycles and needs replaced