I've done it many times. Clamp the gunwales on with a few less than ten thousand clamps and epoxy putty. Use a tapered spacer in the middle, perhaps 1-1/8" thick that tapers to a point at both ends, so the gunwales are spaced that far apart in the middle. So you can bore hole for oarlock pins in one or two places. You might have to cut saw kerfs almost but not all the way through the fat spacer, so it will bend. It depends on the boat. If so fill the kerfs with putty before clamping it all together.
A solid two piece gunwale with a solid spacer is the second strongest there is. A solid gunwale laminated in place out of lots of thin strips is the strongest of all.
After the glue is hard sand it all smooth and put one layer of 6" inch wide tape over top the solid gunwale. Now it's there for the long term.
There is a boat for sale right now (search for Victor Colvard's boat) that I made that way something like 35 years ago. It looks as good now as the day I sold it.