Classic/Antique Car Repair: Rear axle seal leaking, rear axle assemblies, bearing retainers

Question
Brad,
I have a 72 Dodge Demon 340. I bought it new and therefore I know that it has not been modified. The rear axle seal is leaking axle oil on the brakes. I have the service manual and it states that the inner seal has failed. If I can get them, I would like to replace both the inner and outer seals as they are now 36 years old. The first problem that I have is that the manual lists 7-1/4 in.  8 1/4 in. and 8 3/4 in rear axle assemblies. However it does not state how to identify which one is in my car. The only thing I know about it is that it is a Sure Grip Differential and that the axle comes out by just removing the bolts on the backing plate. So, I can't order the parts until I can Identify what size it is. I was reading your previous post about a 69 Suiperbee and you use a pipe nipple to seat the new seal. Will this same procedure work on mine? I was going to have a local repair shop do the work but he told me that it would have two lock rings and would need a press to remove and install the new ones. His press would not fit it and he could not get the parts. I found a web site that sells a Rear Axle Bearing Set that " was specifically designed to eliminate the production bearing retainers and axle end play adjuster" Would this be what I need? Any advice and help would be welcome. Thank You in Advance....Jack

Answer
Ok, here is the way to tell the difference. The 7 1/4 is used on 69 and 70 six cylinder cars and has 9 bolts holding the rear cover on. It also had a filler plug in the cover. The 8 1/4 inch unit had 10 bolts on the rear cover and did not have a filler plug on the cover. The 8 3/4 inch unit had a rear cover welded to the rear axle.  THE 9 1/4 and 9 3/4 inch axles had 10 bolts attaching the cover and had filler plugs on the covers. The pipe method will work on the inner seals and yes you will need to press off the bearings to change outer seals.
Brad