OK. Things to consider. I didn't get back to the forum all day because I was yarding out the old (53)rear end and putting in the 55.1

I wound up using the springs out of the 53 as the eyes on the front of the springs on the 55.1 were egg shaped from Lord knows how many years of being loose and pounding. A little welding and grinding made the stud on the 53 springs a larger diameter to fit more snugly into the locating hole.

Re. the emergency brake setup:
I thought about switching out the backing plates but looked at the rivets and thought about grinding off 16 rivets and passed on that plus I would have had to pull the axles and couldn't remember if you have to pull the back off the 3rd member and pull out the little clips or could just put the drums on backward and use them as pullers.

It seemed easier to use the 55.1 ebrake cables by shortening them and putting 53 type fittings on the cable ends. That sounds like what Nifty 50 2 did.
I took an e-brake cable from the 53 to use as a model and both from the 55.1 which are longer. I will take them to a brake place and have the 55.1 cable trimmed to the length of the 53 and a threaded rod swedged onto the cable end and a couple of new clevises and pins and think that will work OK. I believe I can clamp the 55.1 cable shields using the clamping fitting on the 53 that sits about 7 in. or so behind the rod that runs from side to side and pulls the cables tight when the e brake is applied.

The other issue and a small one at that is that the main brake line on the 53 hooked up to the brake line on the rear end about 1/3 of the way across while the 55.1 connects to the main line right in the center so I will have to run a longer brake line from the frame to the center and then hook up via the rubber brake hose in the middle. Brake line is easy enough to run and flare so just another sub-project to the rear end swap.

Thanks for the advice. Never thought of going to a sailing shop to get fittings and swedge them to the cable.
Jerry