Now the 441 was being raced long before 66 so the technology existed and that is the argument that has meant the that the forward thinking rest of the world allows the B44.
It (the production 441 the public could buy and race) only came out middle of 1965 or just after the Earls Court show as Firko says. Every '441' before this were special works models built from modified B40/C15 parts initially and then pre production works bikes. They were not all 441cc either. The early works bikes were 420cc. Half way through 64 the 420cc special was made into approx 441 (there is no 100% definite specs) and they made stronger cases, and it was still a special one off/works engine, very far from being production model the public could race around on in 64!. These exact details are a little vauge as Jeff Smith himself and the guys that built his engines could not/dont 100% remember and the details are lost. I am only quoting whats in VMX mag. Only Jeff Smith had these BSA's. The public could not have one till half way through 65 and they were 1966 models. In my eyes the rest of the world is wrong in allowing them in pre 65. And the ones you do see racing, in UK especially are far from the B44's that were raced back then anyway.
So going on the fact that there was a couple works engines that were approx 441cc during mid way of 64, i dont think is any basis to push to allow production 66 model 441's to be in pre 65. It totally does not make sense to me if the idea of VMX is to re-create the period.
Yes i know what your saying supersenior.
Just some info to add above, the 441
prototype was shown at a earls court show in november 64. Jeff smith used a basicially standard 441 engine for the 65 season and had won the 65 championship by July 65. After that he used a standard GP (engine and frame) for the remaing GP's of 65 because he had already won and was offered a 'bonus' if he could win on a standard machine. So according to Firko the actual release to the public of the 65 model was easter 1965, when Jeff smith had just about wrapped up the World championship.