I've done similar on a flint smoothbore I built over 20 years ago. When i drilled for my front lock bolt, the hole went right through the ramrod hole. I screwed a brass threaded insert into the wood under the sideplate where the front lock bolt would normally go, shortened and threaded a lock bolt and screwed it in. I screwed in a dummy lock bolt end in the front of the lock plate and peined it over on the inside so that it wouldn't loosen. The gun looks as it should, and I never had any trouble only using the one lock bolt.
Kevin