How much advantage in adding rear disk brakes?

My car does not have rear discs. She is a streeter.
She has 235/60-14s up front and 295/50-15s out back.
She has the KH 4-piston calipers up front and 10X2 drums in the back.
I gutted my P-valve, and adjusted the rear "proportioning", by changing the w/c's to 7/8s, then to 15/16.
She stops real nice with the front-end only diving a little (1.03 bars and HD Munroes)
The whole car just digs, how I imagine throwing out a parachute would feel like.
But; I wear out rear shoes about two to three times more often than the fronts, which is by design, cuz I have plenty of shoes and only one spare set of new pads left.
But I also have an 11/1 360 with a 4-speed so, you-know, plenty of compression braking.

BTW; the rear self adjusters, in the factory system, should not be self adjusting under light braking. The P-valve is actually a hold-off valve, so it takes a good amount of pedal to get the rear shoes
moving, and even more to get a click of adjustment. I run NO Proportioning at all and have never had an issue, and I back up every time I back out of my carport, ending in a 90* turn. I never give the brakes a second thought.
IMO, warning; OPINION coming;
To you guys with adjuster issues;
I'd be willing to bet that you guys are running automatics, and probably "built" ones and IMO, probably need to idle your engines down so they don't bang into gear and/or pull so hard. And before you say that your big cam monster street engine won't idle any slower; if it's smaller than [email protected]; that's malarkey. My [email protected] PurpleCam would idle down to 550 still pulling itself in First gear with an A833 and 3.55s.
Some of you just insist on running mountains of timing, because you can get away with it. Well here is just one example of why not to. I mean why do you feel the need to run 18 to 25 degrees of more of IdleTiming, with a 2400 or more stall, hmmmmm? Do you think the springs might not be able to keep up, lol. I don't get it, and I don't tune that way. Furthermore;
Ma Mopar put a wavy-spring in the Hi-drum for a reason. And a spring on the L/R servo for another reason. But you know, your "built trans" guy, probably left the one on the build-table and probably never gave the other any thought.
Anyway, this ain't helping the OP, sorry for the sidebar.