I'm trying to do the same thing with my Plymouth P15. As usual I get to do it twice, once to learn, and once correctly.
Here is what I've learned: Once you have removed the drive shaft (easy, 8 bolts) in order to remove the transmission ( a transmission jack is really necessary), in order to remove the clutch and flywheel, you are ready to tackle the seals. Note that there is not enough clearance to remove the flywheel unless you tap the bolts in until they bottom out (you will gain the magic half inch that you need in order to remove the flywheel).
With your dominant arm through the hole that the transmission used to occupy, and the other arm up through the bottom of the bell housing, you can get a wrench on the three bolts holding the top half of the seal in place. There is minimal clearance because there is a flange on the crankshaft that obscures the bolts, but by dicking around, you can do it. the bottom half is simpler.
The stinker is replacing the top half !! Here is what I have done. First saw your wrench in half so that you have room to move it around in the close quarters. (The bolts are only torqued to 10 ft lbs so they are not tight.). Next, take a small dowel (3/4 inch) and sand it into an oval. You are going to use this as a cam to hold the seal in place while you use your hands to start the bolts. Count on taking a lot of time to line up the holes because you cannot see up there.
So...looking at the upper seal there are three bolt holes, one east, one west, and one north. Start either the east or west first. line up the hole, put in your dowel cam and twist it to hold the seal in place. Now get the bolt roughly in place. use one of your stiffer feeler gauges against the cap of the bolt to push it against the receiving threads and carefully use your cut-off wrench to turn the bolt and catch the threads. Next, do the same to the other east/west bolt. this is complicated because the seal is springy and has to be held down against the crankshaft (but you have one pivot bolt in place already). Compress it with one hand and use your cam to hold it in place while you start the bolt. With two in place, the third (north, is possible)
Now the Lower Seal. Take the pan off and remove the rear bearing journal (yes, you have to because the seal is slightly egg shaped and the bottom must be slid up and compressed against the upper. The only way to do it is to attach it to the lower journal and use the act of tightening the journal to slide the lower seal up to and against the upper seal.
patience
