Normally I wouldn't have modern outer seals for the rear axle since I think the more flexible inner neoprene seals are more important - and when the differential lube is stopped from diluting the outer bearing grease, the original outer felt seals would be sufficient.

But then I bought this "restored" rear axle with outer seals in place.. Ok, it actually really seems like it was repaired at some time, but it's been rolling many a miles since then + the outer bearing surfaces on the axles were worn out. Modern outer seals can't take much radial play, so the outer seals were shot.
This is the cast type, don't know if any of the vendors still sells this type? Mac's looks similar: http://macsautoparts.com/model-t-ford-rear-outer-grease-seals-aluminum-housing-t2510am/camid/MDT/cp/JS0R3CHL1107029/

The caliper shows 1.560" outer diameter where new seals should fit. The axles are about 1.060" at the outer bearing surface.

An online search gave a fitting seal from Chicago Rawhide - CR 9894. They're supposed to cover axle diameters from 1" to 1.060" and have the right outer diameter and width.
Few bearing houses over here has inch dimensions in stock so I checked ebay - got lucky & found a couple of the right type seal for an acceptable price & shipping cost - got here in a week & that's fast!
Here's with the new seal installed:

But there's more to fix until the axle can go together..

I have used those same outer seals but as you say, they are not needed if you use the modern inner seals like Steve Jelf used in his video.
I never though about it that way before, now they are just an extra unneeded expense.

They are still needed if you get over excited about adding more grease to the roller bearings than they can hold and end up with grease forced out by the path of least resistance. The felt. How much grease is to much? Now I know. I got to gain experience in relining the brake linings though.