I am just finishing building my B31 400cc named "Stargazer"
It is a 1955 swingarm frame, Alloy engine plates, Pearson crank with Carillo rod, Triumph T140 piston, Power dynamo electronic magdyno, 5 speed Nova gearbox, modified Suzuki clutch, home made electric start, ABSAF vernier 2442/2446 cams, ABSAF high volume oil pump, alloy rims, stainless spokes, stainless bolts everywhere (the only external non stainless fasteners are the cylinder holding down studs), stainless mudguards, 520 O ring chain, Replica Robinson 4LS front brake and a Holtworks alloy tank is on order
(https://www.bsaownersclub.co.uk/forum/proxy.php?request=http%3A%2F%2Fi224.photobucket.com%2Falbums%2Fdd149%2Farhigham%2FMobile%2520Uploads%2F20170125_172118_zpsnjdtypfb.jpg&hash=ad38873957519e0e8e489a2e35a5cb55d4562ddd)
And my B31 is called......B31! Seen here on Haggs Mine at the Beamish Trophy Trial and out on a run.
Looking good, have you more images of the whole of the bike?