There should be an option to take it in and have the serial number confirmed. We recently sold a trailer and the number on the title was wrong so it had to be confirmed by someone from the DMV by looking at the trailer.
The problem is without a title, they may not be willing to plate it until you can prove you own it with a title in hand. Best bet would be to go to the prior owner and ask him to order a replacement title. Of course, with a 1968 trailer, did he buy it cheap without a title so the chain of ownership is long lost?
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV