Rear engine seal replacement

Yes, but it's helpful to have some special tools. Some other brands used a one-piece round seal. It was a rubber lip seal in a metal ring. To get those off, you had to separate the engine from the transmission, then remove the flex plate or flywheel. Chrysler used a two-piece rope seal. Remove the oil pan, then the rear bearing, and you'll see half of the seal in the bearing cap. You might be able to use a small needle-nose pliers to grab the end of the half that sits above the crankshaft journal, then push on the other end with a blunt tool like a small punch.

The special tool for installing a new rope seal is a "Chinese finger" type of tool that is placed around the end of the seal, then that tool is pulled over the crank journal first, then the seal gets pulled in with it. The seal is long enough to pull all of the tool out, then you cut off the excess rope.

You can also get a two-piece rubber lip seal for Chrysler engines. You might be able to slide the upper half in by pushing on it, but be sure to oil it first. A better option would be to use Silicone Spray Lube on the seal. We didn't have that stuff in the '70s. That makes rubber parts slide onto metal parts real easily.

If everything is original, the transmission's front pump seal is going to be hardened, and it will crack and leak if weight is placed on it. Changing that seal does require the engine and transmission to be separated. It's easier to remove the transmission.

I wouldn't bother trying to lower the crankshaft. The front can't drop because it's held up by the timing chain and front seal. The rear will be held up by the torque converter. The old seal is pretty tough. You should be able to drag it out with a needle nose pliers.

As a point of interest, a lot of oil leaks start when changing brands of engine oil, especially when switching to some of the synthetics. Often the additives are not compatible. For these engines that call for five quarts of oil during a routine oil change, there is actually seven quarts in there. Two quarts in the passages never drain out, so those additives are still in there. The detergents in some brands will attack the seal conditioners and dispersants in the old oil. I had two students develop really bad oil leaks right after switching to synthetic oil. After switching back to regular oil, both leaks slowed down a lot over the next couple of months, but they never dried up completely.