adding pass side tank to the 81

[Fast68Chevy]

i have an 81 fleetside 2wd and im adding pass side tank to the truck mainly cuz driver side has a hole in it at bottom front

i have two tanks to choose from: a 74 one and a 78 one, i found out tht 73 and 74 have smaller fuel filler tube than 75-78 do and the filler hoses differ also cuz of this.

the 74 tank has 1 3/8" filler and the 78 one has 1 3/4" filler, i checked out a 69 ford tank i have and it has about 1 15/16" filler so parts off it arent gonna help me, too bad though, the rubber butt connector on it would have been great to have and use,,,

i took the 74 tank to local radiator shop to have him block off the existing filler hole and move it to close to center of tank on outside side so i can run off that up striaght through bed floor up to top of bed rail. and also he is gonna change it to 1 1/2" and also move the 5/8" vent connection too.

anyone knopw wher ei can find any 5/8" fuel hose and any 1 1/2" fuel hose ? i went to a local truck repair place to ask them what they do for hose and they said they just use radiator hose, even thoguh its not meant for this, they said theyve never had a problem with it.


what would you guys do, or what have you done in the past or what do you think i should do ?

also what about finding a dual tank switcher valve assembly and how to route lines to make it work ? i know there has to be a 3/8" crossover tube i believe.

LMC catalog illustrations are not being helpful at this point


thanks for anything