Hi , just few simple tips, stick with IMPCO, search the wreckers in your area and get:
--CA 125 mixer $40.
--J or L model coverter (L is more sesitive for a better cruise mixture) $80-$100
--a second hand tank (check date is less than ten years old) $50- $150.
and dont get a multi valve tank(cost more to get tested)
-- some gas fitters will make up lines for you for about $300
-- a gas lock off, a safety relay and some simple wiring and your away!!!

Ive done two 1200 ute`s like this. and both get great mileage..
All the best