I have an 87 long bed that is backhalfed and 4 linked. I put the fuel cell in the bed of the truck near the tailgate, in the center of the bed.
Located my mounting holes and drilled them out.
Cut 4 pieces of 1 inch metal tubing and painted them
Place the 4 inch metal tubing between the gas tank mounting brackets and the top of the bed floor.
Installed 4 5 1/2 inch blots through each hole and secures with flat washers top and bottom and, lock nut and nut.
installed my 90 degree fittings and marked bed floor for installation of fuel line holes. I drilled the holes 1/2 inch bigger than my braided line, installed the fuel line through truck bed floor and installed round rubber graments onto the bed metal to prevent fuel line wear.
Battery box installed on passenger side of bed next to fuel cell..
Worked out pretty good for me..