You can bypass the RWAL solenoid completely. We did it in my 91 dually. Only regret is not doing it sooner. I dont know if the line coming from the front is a direct hook up to the rubber brake line going to the axle, or if you'll need an adaptor. On the D80 I put in my 92, it appears to be a direct fit.
May also post in 1st Gen forum for better exposure. I havent been into this forum in a couple weeks.