You guys are mixing Production part numbers and service part numbers. The 1108338 is the production part number for an L48 with all standard transmissions and late production powerglide transmissions (service part number is 1108418). The 1108420 is the production number for late production TH350 equipped L48s (service part is the same). Production number is 1108361 for all early production automatics (service part number is also 1108361). All of these starters will have the production part number stamped on them even if they are a service part (ie if you had an 1108418, the box label would say 1108418 but the starter would be stamped 1108338)
Difference between the 361 and 338 starters is the solenoid assembly housing drive (nose peice) and drive assembly (more or less teeth). The 420 has the same solenoid and housing drive as the 361 and the same drive assembly as the 338, but it has a different armature than either the 361 or 338 (more torque?). There are a few other small part differences between the 3 different starters as well.
I don't know where the production break occured on these starters. Delco notes them as first jobs, and after jobs, but because the nose peice changed I would ASSUME it was around the time the blocks with the offset starter holes came online (3970010).
1108367 is a production part number for a 68 302 or 327/210HP, or a 69 302, 307, and 327, or a 1970 307 starter.
The 1108418 mentioned above is the production number for a 69 396 (all transmissions), and a 70 396 and 454 with standard transmission starter. Service part is 1108400.
Source is the 67-72 721A Camaro Master Parts Manual Section 2.0 Starter Assemblies.