Hello Mike,
Not sure what is on your guitar right now but I assume they are the 6-on-a-plate tuners that you will find on pretty much all of the mid-line 12-strings from that period.
If authenticity is not a priority I would suggest mounting a set of Schaller M-6 Mini machines.
These tuners became standard on the F-212XL around 1976, so you're not that far off.
The only thing is that the Schaller tuners need a 10 mm hole in the headstock, so you might want somebody with the proper tools do the job for you.
Ask Don ( dklsplace , our host) if he has them in stock. If not he can probably order them for you.
You will need two sets of 3 left/ 3 right.
If Don can't help you, just get back here and I'll tell you where you can get them.
Good luck!
Hans Moust
http://www.guitarsgalore.nl