Originally Posted by 1968BSA
giving the engine number I think would help a lot.

It has been modified in some sort of way, but i would take a plunge and say its a "lightning rocket"

Handle bars are original, and the back rail, looks like an OEM aftermarket accessory - sold by bsa at the time. So is (i think) the engine crash bars.

tank, side panels and carbs are right for a LR, but you may want rid of the cola shaker silencers in preference for something a little more in tune with the bike.

I think the original colour would have been yellow. Black headlight and number plate. (full mudguard, this has been chopped)

It wouldn't cost a fortune on cosmetics to put it as standard, (depends on engine condition) or use as is.

The chromed covers on the air filter are quite rare now, the original filter bodies had holes all over and allowed water to get in, this was the cure. later on the covers remained un-drilled at the top to keep the water out, but I think this idea looks more practical.

Wow, small world. I just posted my '65 T-bolt. The PO told me the bike had this huge rail on the back that he threw out (it's killin me) but he saved the plaque off it that said BSA and I got that with the bike. I see you have the same plaque on yours. Not many of those around from what I can tell.
Nice bike and great family heritage you have there.