68 dart gas tank leak

Thanks. I’m sure the gauges have an issue with that module mentioned in another thread as both the fuel and temp don’t read. Right now I’m interested in gettin the leak stopped so it can be driven. The local parts store doesn’t have just the seal.

I contacted the sellers online of the senders and they said there are 3/8” size lines and 5/16”? Is that true? I would assume they would’ve made one sander for all of these darts in 1968.