if you're leaking fuel and the tank is new, i'd suspect the fuel neck tank grommet or the sending unit gasket.
https://www.detroitmuscletechnologi...-64-73-fuel-gas-tank-grommet-2203472-2880481/
https://www.detroitmuscletechnologi...-tank-seal-and-ss-lock-ring-locking-retainer/
also, obviously, if you have any type of aux fuel pump check all the lines. sounds like these dudes were sloppy or lazy or both so it might just be loose fitting/clamps. thankfully all of that is easily remedied.