Would it be possible to modify a standard frame?
Yes, it certainly is possible, the only reason for the dogleg in the downtube is for the hotsy-totsy carbs and in some cases the bell mouth intakes. The Dogleg serves no other purpose, other than that, Im sure there is some unusual tabs or bolt bosses and certainly more oil capacity but by & large the bike is merely a hot rodded Golden flash. Certainly easy to duplicate. It should be noted that many people had the opinion that it made the bike fast enough to be a tad bit frightening to ride, although to be fair, the Sprung hub Triumph was similar in challenging traits at high speeds.
But my frame was modified and there is pictures of it in a thread here. Still not 100% certain but we believe it was modified by Kenny Eggers to be similar to the factory race bikes he often rode. Its also likely it was someone he was associated with who did the work to my frame, but regardless I believe my project was at one time a bike owned by Eggers.
As to Dutches comments, YES,, the breakdown has been documented how many were produced and where they were shipped (2 IIRC went to South Africa?) Its also discussed here. But not many were made, fewer still survive. The Salient point is they were a stop gap factory performance bike, mostly to satisfy US demands for a sports-racing model and were never intended to be a long running production.
**** EDIT, the photos I just posted here and elsewhere here on this forum are of Eggers rigid frame race bikes, that is because, most of the photos I have gleaned are of his factory race bike which was a rigid, not a plunger, but had the same Dogleg modification that the factory did on the Plunger/Sprung Superflash frames. A small but important distinction.
Study the pictures of my modified rigid frame I have on a seperate topic,, Its been determined that its unlikely my frame had the dogleg modified at the factory, but we have not ruled it out either, But it has been well done whoever did it.
#### I had planned to build a "Hot-Flash" modified Golden Flash with late crank and rods, hot cam, alloy head, higher comp pistons and improved oiling, But that plan changed when I got the rigid race frame and evolved,. I have posted extensively on that topic here. Still on the back burner, but its still on the agenda.
My project has also been checked out by a few other BSA experts including BritTwit. I have had several offers to sell it.