Gas tank relocation

[Smitty52]

when i bought my truck the gas tank had been relocated to under the bed and i was told the gas tank is from a seventys mustang. I want to put a fuel cell in instead because the tank is old and it looks like jb weld was used to mend holes in several spots and was wondering if anybody out there has already done something like this or plans on doing this and has any pointers or places to look for the parts. Thanks