I have looked at Rocky Mountain Brakes $869 and seems there are problems backing up.
If you are backing up at 40MPH, or are trying to hold on a steep hill, you will definitely find modern Rocky brakes lacking. That's why you keep your transmission brake and original parking brake functioning. The only time Rocky's truly lack stopping power is when they're wet. When they're dry, and you're traveling forward, they work great.
If you want to be able to lock up the brakes under any circumstances, the only commercial option would be disk brakes. I personally find them to look horrible and since I drive my car at the speed it was designed for, do not typically drive in rain, and do not live in a rabbit-warren of a city, I find original brakes sufficient and suits my sense of aesthetics. It really depends on if you want early 20th century technology or late 20th century technology and only you can make that decision. There are some pretty decent looking custom drum brake conversions but it doesn't sound like you're looking to fabricate something yourself so you're back to disks, unless you wish to pursue making your parking brake a service brake and that is not really difficult custom work as there are kits, and they work pretty good.
As disks become more the norm, I've found during tours that drivers become stupider and stupider, pulling stunts with their cars that no stock "T" can match and thus become a hazard to drivers who have restored their cars. If you go to disks and are surrounded by other "T"s, do not forget that your worry about your motometer may in fact become a rear-end reality. Remain conscious of the guy behind you. For that and a couple other lesser reasons, I have lost almost all interest in organized tours. I used to look forward to tours to be "equally yoked" with other drivers of similar antique cars. That is definitely not the case anymore.
