The norm is for the locks to be common on the first few months of '66 production. The rules are not clear-cut on the matter, but to avoid any chance of losing points, it would be best to stick with what is considered more common for that time period, which would be ramp-lok. Remember that the rules are a guide to help the judges, they are not forbidden to step outside of what is explicitly called out on the sheets.
Of course, with some research and documentation, enough compelling evidence could be presented to sway the opinion of the judges and possibly make an update to the rulebook.