The repop tanks i've seen are pretty thin.. I don't know how you'd tap a piece of thin sheetmetal.
Depending on the tank design, and how skinny your (or the neighbor kids) arms are, you might be able to pull the sending unit out to give you a large access hole to the inside of the tank, then hog out the fuel supply hole to put in a standard adapter and put a washer and nut on the inside to hold it on/give it something solid to thread into.
I've not ever looked for one to know if such a thing exsists, but maybe you could find an adapter to go from metric to standard?
All in all it's alot of crap for an outfit to sell you a part for a 50 year old american truck that has METRIC threads on it.. I mean, at the very least, if the part isn't going to be a bolt in replacement, they should say so in the product description.
