Rear Disk Conversion, is it worth it?

Hey, haven't been here in a while but I am thinking about upgrading the rear brakes on my 74 barracuda from drum to disk. It has front disks.The stopping is ok, but the drums are worn and now the proportioning valve is faulty. Anyway, I was wondering if there would be a significant change in braking?
The whole braking system is new except for the proportioning valve, booster, and drums.I did order some ceramic pads for the front and was thinking of replacing the rubber hoses with stainless and stopping there.
Thanks.

Not from what you have shared so far.

Based on some testing we did with Tim's road race car I'd say that rear discs aren't required until the car goes over 150 mph. Below 150 mph rear drums are probably a better design. The OEMs have moved away from drum brakes these days but I think they have other reasons for that. I think they use 4 wheel discs primarily because of ABS requirements.

There are gains.
If it is set up properly with decent parts, you'll get less rear wheel lockup. They will fade less in heavy usage.
I went from 12" front disc/10" rear drum to rear 10.7 disc. There were no improvements in braking distances but at that time, I hadn't really found the limits of the rear brakes. Servicing was easier with the discs.
Remember, a 4 wheel disc setup uses NO proportioning valve but can use a distribution block. It is the size of the calipers that determine the proportioning. I have 2.6 piston calipers up front and 1.5 piston calipers on the back. You always need the fronts to be bigger since the front does 65-70% of the braking.

Rear discs do save weight, that was the big reason we switched on Tim's Valiant. The car didn't stop any better but it saved weight and the braking was a little more linear. Drum brakes are non-linear and you can get in trouble in a race car with drum brakes if you aren't careful. For a street car I think the drum brake is a better design since the parking brake is dead simple. But having said that, my street cars all have 4 wheel disc brakes so I don't follow that advice myself. I do sort of regret switching to disc brakes on the rear of my Coronet. That car had the big station wagon drum brakes on it and it stopped on a dime. The parking brake also worked fantastic. The parking brake I have now doesn't work very well and the brakes don't feel as solid as they did when the car was disc/drum.

OP, please note when you lock the tires on any one axle, there mainly only two potential shortcomings in your system, your F/R brake balance is off, or you need more tire on the locking axle. Pretty simple.

My rear discs are 90% aesthetics and 10% "performance" when I really do put some heat into them.

"Worth it" is dependent on what you are after, a street car with minimal performance braking won't benefit much at all.

My brother's car has them and it stops no better from close to 120 down the drag strip than it did with discs up front and drums in the rear. I think I would get the best front brakes I could first before looking at the rear discs.

If you look at motocross bikes they always upgrade the front disc rotor, master cylinder, cable etc and typically leave the rear disc brake alone. Having a powerful front brake is a big advantage.

We cannot forget the limiting factor in braking distance is tire friction. 4 wheel dis brakes will be lighter, have subjectively better brake pedal feel and linearity in application, but will not directly result in reduced stopping distance. Of course as repeated stops are made the disc brakes higher ability to dissipate heat and resist fade will come into play.

That is true. For any car that is going to be driven hard the first step would be to upgrade to a 13 inch rotor up front. I drove my Coronet for years with 13 inch rotors up front and the big 11 inch drums out back. That combo worked great and was fairly simple and inexpensive.

Fixed it for you.

Thanks everyone!
Based on what I'm reading here and from other research I've done online I've decided to keep the rear drums. As I said I ordered EBC ceramic pads and just ordered stainless hoses front and rear. Also called Mr Moparts and found a proportioning valve.
Also since the warning light came on related to the valve, I took a look at the wheel calipers and cylinders and decided to replace both front calipers. I never liked the ones I got from Pep Boys years ago. They did not come with guide pins so I used the old ones. They also didn't come with the retaining clip and the existing ones didn't have one so I didn't even know it was missing.
I'll probably end up taking the whole system apart and clean re-lube the rear brake shoe contact points etc...I bought some permatex silicone/ceramic lube.
This car is just a cruising car just fyi.

Its not often here somebody actually asks for advice and listens, instead of heading down the path they were set on in the first place.

Here is the new rear disc setup for my Duster. Baer 13 inch rotors with 17 inch Weld wheels and drag radials. These rear brakes are mostly for looks. They'll work nice but I don't really need 13 inch rotors on the rear. A drum brake would probably work fine for this car since max speed is about 125 mph. A 10 inch disc brake would also work but would look wimpy so I went with the big 13 inch rotor.

This is a pretty loaded question without knowing what you expect from the car.

I had a Mustang that I ran on the road coarse. It was a 93 with factory 11" discs in front and 10" drum in the rear. Probably will stop better than any factory muscle Mopar with OEM front disc and I was pretty content with them on the street. Until I put it on the Toronto Motorsports Roadcourse. Factory brakes were absolutely cooked after 3 laps. Brake fluid boiled to a point I had no front brakes.
Upgraded to 13" dual piston in the front and 11" rear. The braking power in this 3300lb car was awesome. It could go 10 laps without overheating the brakes. I could notice a slight downgrade after 10 laps but still excellent. I was tired before the brakes were. Then I road in the same car with 13 in all 4 corners. Brakes were supercar level.

After the initial upgrade from drums to small front disc. This will allow for modulation and a big improvement over stock drums but after that it's just how much do you abuse your brakes. All of this does not apply if you run tiny tires.