I use these on the Lambo.........
https://www.ebay.co.uk/p/Tow-Ball-Swan-Neck-to-Flange-Converter-BR-S2f-by-Bak-rak/15008786818?iid=182806815925&chn=ps
No owners club, That's why we advised above to use the VMCC who will cover this bike and supply a age certificate.. List here of DVLA approved clubs. Nothing for Montesa.. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/733199/v765x1-list-of-vehicle-owners-clubs.pdf
My bikes have been checked by SGS just to make sure the VIN was clear and not been tampered with. They also wanted to check the bike was in standard spec to make sure a age related plate was suitable for the bike. If the bike has been modifed it won't get a age related plate. Every bike must have a NOVA number record on the sytem or the DVLA won't except it. Just about every post says on registering a bike says you need a NOVA number, This has been the case since April 2013. Simple as that, even if no duty was due.. The V5C arrived within a week.
New one on ebay and trials and tribulations are showing stock !!! https://www.ebay.co.uk/itm/SIDE-STAND-LEG-ARM-PROP-BETA-REV-3/123244125340?hash=item1cb1ec1c9c:g:4FAAAMXQDjhQ5t2n
Stu at Trials Day is the best with bikes supplied in various sizes, Most of the others you have to have your own bike........ Worth the trip !00%and the land is amazing. https://www.trials-school.co.uk/
As i said, The V62 will be fine as he has a registration number already, just needs to pay his £25.00 and done, May even get it back. No need for all the other advice on what you don't need to do as that makes it more complex than it needs to be.!......... Worked many years with the DVLA......
The DVLA will accept Bultaco UK for dating letters even though they are not listed as an
owners club. The DVLA see them as a UK Bultaco original subsidiary.... But it's not a problem as the V62 will be fine as already stated.
As you have the registration number all you need to do is fill out this form (V62) and pay your £25.00. It can be downloaded from the DVLA site below........... You don't need owners clubs or anything else as the bike already has a reg number. They may even refund your £25.00 depending on the reason you give.... Simples.
https://www.gov.uk/government/publications/application-for-a-vehicle-registration-certificate