botboy,
Youwont fit those tanks at the back of the bed, use a sub/blazer tank and convert it. and you wont be able to have the filler behind the liscense plate(too low) but there are easy ways to rig up a filler.
the fuel pumps pressure you would drop using and external regulator at the motor. holley, barrygrant, and a few others make regulators that would work. If you lower the pumps voltage you will burn the pumps up faster. they are not designed to run a a lower voltage.
As far as ASE you can go to this link to check out more info and cost
National Institute for Automotive Service Excellence
first test are more expensive than recertification. but it[ase] at least lets me know that I KNOW what I am talking about(most of the time)