I understand this topic might best go elsewhere,, But chking profile, I dont see it resurfacing. Not looking to add insult to injury for mods... But to answer your question on the petrol tank,, gas tank to us Americans...
I have the exact same tank, as well as a number of other period fiberglass tanks, trackmaster, cafe, etc etc...
Some of which get the period-patina crowd all worked up in a hot lather...
I can send off list, or post a series of pix in misc off topic if there is interest,, But I DO have an exact version of that tank, albeit, not the cool gas cap. My understanding is its a period aftermarket tank availible via period vendors and shops. DommiRacer also trade name "Accessory Mart" in Ohio, had stuff like it back in the day, MAP cycle in Florida also a well known catalog company. I have some period catalogs, and ads from magazines.. lots of old magazines had ads for these types of things in them and takes some sleuth work but you can often ID the maker,,, I have 2 others where the manuf put their business card under the resin and embedded into it., I can post some pictures of this,, interesting small companies no one seems to have heard of.
I am especially interested in period accys and theres currently a lot of excitement about early accy parts, racing, cafe, custom and yes..... CHOPPERS!
For example, I was just talking to a friend today advising him on a 1962-3 BSA A10 project he is purchasing. On the rear fender is one of those dreadful limp sausage tail lights. He couldnt care less if its a period accy or a modern repop.. BUT, and in fact he likes it better than the stock license plate mount and tail light..
But I told him at some point to check.
The repops dont say anything or say Made in Japan,, But the original accy tail light casting says "Made in England" and THOSE are worth a small fortune to the patina hipster crowd. AND to period customizers.. Even BSA importer in Nutley New Jersey peddled them with a period Bates headlight and bracket as part of a
BSA "Lighting accy kit" and those are highly coveted today. * i have one of these kits and using it on my BSA Goldstar scrambler.
I got a cool set of period Bates seats as well, Doesnt mean much to the rivet counters and OCD bolt polishers but for "Survivor Bikes" with period custom accys,, Its very exciting. Funny thing is, its stuff people thought to be rubbish and threw away, now? $$$$$$$$$ Who knew? Heck I have tossed some of that stuff myself, had no idea people would have wanted it these days.
As to your "Bitza Bobber" I think its cool, just needs some work to be functional, and often orphan parts can be put together to see another classic on the road instead of sitting hidden away. I wont cut up or customize a stock bike, but do appreciate seeing fun bikes on the road.