Thanks for the welcome.
Conquest- the kit that we make for a 1996 E-350 would require four holes to be drilled through the side of the frame two per each side of the RV. The brackets provide clearance holes to line up the new holes onto.
The kit you would need is 57138, you can find the manual for it in the link below. You can look over the instructions and see if you feel comfortable with the amount of drilling required.
As for price, we suggest that you purchase the product through one of our retailers or locate a dealer near you.
Dealer Locator | Air Lift Company
In order to keep within your $500 budget, you would probably have to go with a manual control system. We do offer these in a dual (separate) configuration.
Air Lift Company Load Controller Dual (Standard Duty Compressor) - Load Support On Board Air Systems
The price listed on our site is suggested retail, if you visit one of our retailers you will most likely find it for a better price.
Also, you may be able to afford a nicer controller by using the $100 rebate
we are currently offering.