Terry
Congratulations on doing the motor transplant & getting your Compact working again. Yours is definitely a unique color & variant for sure, & will be a conversation piece in your collection. It's also nice to keep vacuums that have family history too. I also personally like the Compact PN that's a re-badged Eureka Roto-Matic with the bleeder valve instead of the TriStar PN they lade mater based on the Eureka PN....it seems to me that the brushroll bristles seem to stick out the bottom plate & groom slightly better than the TriStar PN does. And the straight-suction hose with PN cord on the outside would be more reliable & trouble-free long term than the electric hoses would be. The only thing I would suggest, since Eureka Roto-Matic parts are becoming more scarce as time goes on, is I would pick up a spare powerhead internal hose, just to have on hand when it requires replacement. Over time, those hoses will develop cracks & breaks to the point it will affect the vacuum's performance & need replacement.
It's probably best to just throw out the old motor. Sure, they are easy to repair if you wanted to, but they are so inexpensive to replace you're likely to spend at least half what a new motor in parts to repair the old one. Plus, being from the late 1970's, that motor's electrical components have so much wear & tear on them, it has a relatively short life left if it was able to be successfully repaired.
As for that motor that was a higher power version & slightly longer, that is a Ametek 115923 motor the Ebay seller was also offering. Consider yourself lucky you stuck with the Ametek 116311 motor you bought that is original to Compact/TriStar vacuums. That 115923 motor will NOT fit the Compact vacuums, ONLY the TriStar vacuums. The reason is, when you pulled apart your Compact you would have seen the blower end of your vacuum is part of the magnesium body. If you take off the exhaust diffuser, you will see there is a plastic ring riveted in place that has the lugs to attach the exhaust diffuser. In the early 1980's, Compact was turned into a vac shop brand for a short while & the first red two-speed TriStar was introduced. The first TriStar CXL single speed model after that saw the design of the blower port changed, it was no longer built into the metal body but turned into a plastic blower basket riveted in place that has the ring for the exhaust diffuser built in. Those TriStar CXL & DXL canisters after the red two-speed model can take that Ametek 115923 motor, as the blower basket can be trimmed & modified to take that motor.
However, for people that own a Compact, are in need of replacing the motor & want to upgrade it's performance, there is another option available. Electro Motor, the original Aerus Electrolux motor manufacturer, was the motor used in the TriStar EXL. This was changed with the TriStar MG1, though, when Electro Motor was sold off from Aerus. There are 2 versions of that motor available that will fit perfectly into Compact & TriStar vacuums. The LH0274 on the website linked below is the standard replacement motor for Electrolux 2100 canisters, & pulls 100" waterlift, same as the Ametek 115923 does, & is carried by most vac shop suppliers & found on Ebay quite easily. The LH6500SR motor, though, is a HUGE improvement over the Ametek 116311, 115923 & LH0274 motors, though, & pulls a whopping 117" waterlift. Both of these motors are the same dimensions as the Ametek 116311 motor, & should fit perfectly in their place. When installing the new motor, you would have to cut off the wires from the old motor & put on a couple of 3/16 inch female disconnect terminals to connect the new motor. Also be sure to put some Pliobond on the rubber motor mount to be sure that new, much more powerful motor stays in place once installed.
Rob
https://www.centralvacuummotor.com/vacuums/electrolux.htm
https://www.amazon.com/AIRIC-100pcs...pID=31qYqYtz5LL&preST=_SX342_QL70_&dpSrc=srch
https://www.amazon.com/Low-VOC-Plio...pID=51yFPKHpjpL&preST=_SY300_QL70_&dpSrc=srch