Not sure how long this rear gasket and auto trans gasket has been around but got my first look at a Ford 9" gasket the other day. From what i see it looks like it will do a better job at sealing. It reminds me of what OEM Chevy thermostat, fuel pump and water pump gaskets have sprayed on the gasket surface to help seal. I only use GM gaskets for those jobs. These Locker gaskets don't appear to use a paper product for the base material, more like a polymer.
https://www.lubelocker.com/

Will be pulling the 8 1/2" rear sometime soon to change R&P back to a 3.73 and will buy and install a Locker just to see how it works. Never had a seepage problem with LPW cover to housing, but always painted the blue FelPro gasket black before install. Anal, yes.

Not an RTV user for making gaskets, only where only it will work properly, or no know gasket is available. And we know that gear oil and standard RTV don't get along well. You need to use only a gear oil RTV when using gear oil.
Bob