I'm not sure that it would fit onto a modern Handi frame without some work.
If someone wanted to get this, you can get it before having the tax stamp as long as the barrel and frame aren't under the same roof at the same time. I'm no lawyer but that's what I've been told by people in that business. For example, you could bid and buy the barrel and have it shipped to work or to someone else's house as long as they don't own a Handi. You file the paper work, wait for it to be aproved (that's the catch, it has to be aproved) then once you have the aproved form1 with tax stamp stuck to it and overstamped you put your gun together. If you trust the seller, you might even make the purchase and ask them to hold off on shipping while your aplication clears (4 moths or so is a while, but that would be one way to make it happen legally)
That's fairly common with AR type guns. The uppers and lowers interchange and the only difference between an AR pistol receiver and an AR rifle receiver is it's legal definition. If you have an AR rifle and want to put an AR pistol together from parts you either buy the AR pistol receiver first (that being the smart and easy way) or you get the short upper shipped to someplace with no AR rifle on the premisis. You might do it that way if you find a super deal on the upper and have to get it before you get the lower for whatever reason. (or if you get the upper for a SBR while the paper is pending)
Personally, I don't know if I'd go through the effort and expense of the NFA process for a 410 single, but that may be just exactly what somebody wants to do themselves.
