It's as simple is this: Your dual quads is an rpm thing, so you need to do as much as possible to help flow/rpm's. For the budget, I'd use ported 360 heads (you can port at home with a dremel), a bigger cam, and if it's in the budget to bore it, bore it as much as you can safely bore it (sonic test the cylinders). This is about as low budget as you can get.
P.S. If you are not going to spin it over 6500 rpm's, you do not need a steel crank at all. Have a dragway friend that spun his 7200 rpm's for 4 yrs. Cast cranks are lighter and thus will rev faster.