IIR the ABS only works in 2wd anyway and chances are you would be in 4wd in the snow. So swapping to the Chevy cylinders would be a mute point as far as your rwabs operation in 4wd in snow.
As far as locking up, it depends on what you have for weight in the back end. The more weight you have, to a reasonable point, the better you'll get around and stop in both 2wd and 4wd and the less rear lockup you'll experience when braking. I like to have about 1000 up to 1500 lbs in mine in winter.
Note: I have to buy water softener salt pellets for home use anyway. The bags are weatherproof, the contents work well in a pinch for under-tire traction, and I get a slightly better deal buying in bulk (2000 lb pallet) every year at the beginning of winter. So that's what I use. The bonus is my wife does not have to deal with lugging a 50 lb bag of softener salt when she goes grocery shopping. And my traction -- both stop and go -- is greatly enhanced. One other thing about "traction weight": Too many guys use heavy, hard objects like scrap metal or firewood. In the event of an accident, those become deadly missiles. Something 'softer' like bags of salt pellets might save a life.
If you do the conversion to larger cylinders, and do not have the height-sensing proportioning valve (useless junk to be disabled, imo), you might look into an adjustable p-valve like those Wilwood sells. Then you can dial in your own preferred front-to-rear braking under the load you normally have and even adjust it with the turn of a knob if that changes. Unlike the RWAL, it would work in both 2wd and 4wd, but it is not an anti-lock device if you are dependent on those.
But you can go out and find the slickest traction you are likely to encounter - say, ice in winter and loose gravel in summer - and hit your brakes hard enough to lock them up and keep adjusting the rears so they lock up at the same time the fronts do - not earlier. It will always vary depending on load and traction, of course, but you'll get pretty good at knowing where to set the adjustment. What you are doing is putting a real brain and real world conditions in control of a "dummy valve" similar to what the factory put on some rear axles (height sensor).
Those never work well, and not at all if you have good load-leveling suspension. In fact, they work against it and are dangerous since a truck with air bags might be very heavily loaded, yet level, and the dummy valve will restrict rear braking like the truck is empty. They do not "enhance rear braking" when sagging as described earlier, they restrict it when you aren't sagging. There's a difference. And sagging in the rear automatically screws up braking and steering right off the bat.
So-called anti-lock brakes have been around long enough now that many people have difficulty driving a vehicle without functioning anti-lock brakes. They are godsends when they work properly, but I'd never bet my life on them and they're no substitute for skillful non-anti-lock brake technique.
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