I understand your concerns about the brake and steering issue. Here is some info that may help.
1. they didn't come with self adjusters, did you add those or did the PO do that?
2. I know the only time I've had a problem with the stock brakes pulling is when the toe adjustment wasn't correct, have you checked that?
3. I'm not sure what disc conversions are available but there are power/dual master kits.
4. I rebuilt my box twice over the years, still get a little wandering. Part of that is the oversize tires I think. I've just learned to live with it, it's not bad enough to be a safety concern
I'm not against the idea of a later front end for the brake and steering improvements it was just never in my budget.