I would run the 23 degree heads. The 18 and 14 degree are for serious performance high rpm motors. The longer valves are most likely for proper spring height and to get valve train geometry correct. Overall the longer valves won't hurt you, but many of the higher performanc heads often require offset intake rocker arms.
If you can use a victor jr. intake with the heads your offenhauser single plane will also work with the heads it's similar. The heads your looking at are for a high rpm motor, you will loose alot of lower rpm torque.