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

it's fairly straight forward to do. getting the old rope one out is kind of tough. you will need a dent puller with a long *** screw in it. screw it in and have someone turn the crank by hand as you bump it out in the direction of the turning crank. I always use the two piece neoprene seals. offset the seams about a 1/4" or so. before you go to all that trouble check the oil fittings/ oil sending unit on the back of the motor behind the intake. a lot of times they are the bad guys.