If the cam shaft was installed 180 degrees out, I think that would happen. I would not affect the engine operation however. The timing mark on the cam should point at the crank and the one on the crank gear should point up at the cam gear. If they were installed with the cam gear mark pointing up, they would be 180 out. Someone correct me if I am wrong. (page 8-64 of 66 manual)
SWMBO's '66 Coupe 289, 2-V, C-4(Pony Interior, Rally Pac, A/C & Tiffany Stripe) & An absolutely rust free '65 289-2V C-4 coupe project. Now almost done. Only took 13+ years.