If there's room to hide it, you could use a much bigger reserve tank. I'd suggest a 30-lb. Freon drum from your local refrigeration repair shop. They're non-refillable, and most of the shops just discard them when they're empty. Drill a hole in one end big enough to accept a rubber grommet, and use the check valve from a power brake booster, and a 3/8" line to the intake manifold. Then solder a piece of 5/16" steel brake line into the other end, and run your vacuum line to the wiper control from there. Lots of reserve vacuum! Hide the tank under the bed or cab if necessary.
Jerry
