New coaming planks are easy to cut and shape. I made a new set about 10 years ago. They look good and have held up well. The difficult part was making the mahogany blocks that tie the coaming planks into the sides of the cabin. Got it done, but it took way more trial and error work than planned. With hind-sight, it seemed that the port and starboard sides of the Ensign mold must not be as precisely symetrical as we had expected.
Those blocks between the coaming planks and the cabin are pretty stout. Perhaps you could reuse your existing cabin-to-coaming blocks. Alternatively perhaps you can buy them from Ensign Spars or buy serviceable coaming-to-cabin blocks from someone on this forum.
Note: Other parts of that Ensign restoration also confirmed that measurements on the starboard side do not necessarily match similar measurements on the port side. After considering the # of Ensigns produced in the early Pearson years, my restoration partner and I decided that the Pearson motto must have been "Close enough. Ship it"
Good luck.