Seems like many of the 88ish-93 Ram pickups have an issue with the rear brakes being almost non functioning. I have read that the rear ABS unit that is mounted to the left frame rail above the rear diff is to blame. After wearing out front brakes, while the rears shoes are nearly unworn, I decided to replace all the brake wheel cylinders etc with new, remove the ABS unit, and run a brake line directly to the rear brake hose, eliminating the cast iron ABS unit altogether. To my surprise, the rear brakes are still lame. They bleed fine, apply fine, but I cannot get the rear brakes to skid the tires, even on loose gravel. so I am suspecting the brake safety switch/brake divider block, mounted below the master cylinder may be to blame.
Anyone have the answer to this? I know many 92-93ish Dodge truck owners who have the same issue. Rear brakes just don't have any power

One way increase the apply force of the rear brakes is to increase the rear wheel cylinder size. It was the other way on my 69 Charger when I converted it to disc brakes and left the rear as drums I sometimes had the rear brakes want to lockup so I went from the factory 15/16 rear wheel cylinder size down to 7/8 and eliminated the rear wheel lockup.

I was considering doing this. It has 1" wheel cylinders. But usually pickups have rear brakes that lock too easily.

My 92 Cummins will lock the rear brakes before the fronts. It still has all the RWAL functioning. I installed an adjustable valve in the rear brake line and that has helped. Mine does have rear discs and a hydroboost conversion but it was the same before. My 74 rear brakes aren't worth a crap, even the parking brake is weak. Everything is new except the drums so I'm attributing lack of shoe contact as the culprit there as they worked better before. No one arcs brake shoes anymore so they will either wear in or get replaced with discs before that.

On my dodge truck that has a Dana 70, I used GM 1 ton wheel cylinders. They bolt right in. 1-3/16 bore versus the Dodge’s 1” bore.

I never had a problem with my 92 D350. I put over 300K miles on it mostly with a trailer and did the rear brake job twice.

what model truck and what brake size?

As for why the rear don't grab as well, liability. Manufacturers limit rear braking ability to prevent rear lockup in an empty truck. Helps prevent accidents.

Yours sounds extreme though which makes me wonder if there's not a problem elsewhere. Lots of possible things, bad master, p valve, hose, incorrect install or adjustment of shoes or as mentioned incorrect arc of shoes (this is common nowadays).

It's a 93 W150 with 11x2 1/2" rear drums. This is a very common issue with this era of Dodge trucks. I am considering a change of rear wheel cylinder diameter. I have sevral friends with Dodge trucks of the same vintage, and they all seem to wear out front brakes, and rears barely wear.