67 rear coil springs helper air bags and blazer gas tank

[rcachevy]

i'm still new here but i'm going to give this a shot hopefully i word it correctly.i have a 67 longbed fleetside with 3 in. drop coil springs ,i like having the coils but when loaded they can't handle the load,i bought some airbags that fit inside the coil bot nobody makes a kit for these trucks anymore that i know of so i think i have to drill a hole in the frame to run the air line,so does anybody know of a solution? a kit i overlooked ? coil springs that handle the load better ? i don't really want to bag it and replace the coils.also i have the plastic blazer tank and the steel braided rubber fuel line,has anybody else had trouble with the 10 % ethanol fuel maybe eating away at something,i keep getting black pieces of something in fuel filter to the point where it kills the truck,does anybody still make the old galvanized metal blazer tanks ? thanks for reading my rambling ,Ron