that's not a big issue,the only problem being,you cant change engines without a title.
Maybe is not a big issue were you live. In Florida if you get stopped by a LEO, they will check matching numbers from the registration to the frame. Try to explain then: " but Mr. occiffer, back in the 60's this was the way they titled bikes in other states".
And besides, the law says that the frame number is to be your VIN. This applies for all vehicles on or off road.
And yes, I can change any engine without a title. When you work for a manufacturer and you replace an engine, let's say in you car, the new engine comes without a EIN. The technician gets paid for hammering the numbers with a die (we use to get paid 1.0 hs from Mercedes). Guess what, nobody did it.
When you go to DMV for inspection down here, they go straight for the VIN and if there are any doubts they make you pull the carpets and check one of the hidden VIN's in the car (there are at least two laser etched in the floor).
I know all this may not be relevant to the owner of an SOHC Honda, but there are a lot of people rescuing older hardware out there and they may get discouraged or believe they were screwed when facing situations like this.
It can be done, it just takes time.

Gaucho