FWIW, it is a Sportco front sight base. I think a Sportco barrel would have enough meat to thread for a II** action.
Yes, when the rules changed allowing non-issue pattern rifles for competition, there were all sorts of rifles made up. The practice was to use a Lee Enfield based rifle for long range because of the compensation, and a front lugged rifle for the shorter ranges.
Right now, Switzers has one built up on a P'13 action.
As projects go, there are lots of bubba'd Rosses, Lees, Enfields, Mausers, etc. that can be had cheap.
I can see a seller being cautious about advertising a rifle like this one, because heaven only knows who did what.
A chap I know sold a friend a M1895 Winchester barrelled to .303. Barrel didn't wobble in the receiver because of the epoxy. The cases looked odd; whatever had been used as a reamer wasn't ground to correct shape.