The rifle that I have is a 1970's model Marlin 336. The serial number is next to the tang screw . Now when I look at either Marbles or Lyman tang sight, the screw holes will hit the middle of the number. I have this bad hankering for a tang sight after 40 years. Has anyone come across this problem installing a tang sight on an old Marlin? Neither Marble or Lyman have returned my email.