Here's my 10c
You don't need to pull the engin to chainge the rear main seal.
If you have access to a lift it's quite straight forward to change it in the car.
And if no lift, it is still do able.
Here is the Process (67 dart with auto trans)
NB make sure you have full pan seal kit and full rear main seal kit and some make a gasket rubber sealer for the corners and trickybits.
1) Undew drivers side motor mount, jack up motor about 2 inces, now jam a large socket in by the tranny bolt to keep it there.
2) let down engine, take out dip stick.
3) jack up car, on full lift preferably
4) drain oil
5) take off oil pan (making note of longer pan bolts at back)
6) with pan off, remove bolts to lower half of rear main seal housing. This takes off lower half of seal and L shaped seals off around the housing. INspect.
6) Use a wire or somthing to push to upper part of the seal around the crank and out.
7) now spray everything clean with break cleaner.
put in your new rear manin seals. Which is the two halves of the rear. The top half, push round the crank into place. The lower half goes in the metal peice you just took off. IMPORTANT: the metal peice has little L shaped rubber bits that go on its corners. These need a good dab of rubber gasket compound on them even though they are rubber. This is what the factory did. Then tighten it back up there before it drys.You just chainged ALL of your rear main seal.
9) clean off pan and under side of engine. Scrape off old gasket, blow down with break cleaner.
10) install new gasket kit. Cork goes over rubber, dabs of sealer in all corners. Putt some sealer on the cork strips, leave the fron and back rubbers dry.
11) bolt back up pan, not too tight, not too loose. Don't want to split that cork gasket.
12) lowere down car, jack up motor, take out socket, put back motor mount, put oil back in engine, put dipstick back.
your done
There you go.
Takes about 4 hours with a friend.
Don't rush the cleaning or the gasket putting back.
T