I have a 1967 Rally 6105. Would like to install locking tuners but of course don not want to drill any new holes. Any suggestions on what brand/style will fit this?

I'm not 100% sure, but I think you have a Kluson style mounting on that guitar. It would seem that something like this would make sense:

http://www.amazon.com/Gotoh-Vintage-Kluson-Locking-Machines/dp/B003TL2EWY

http://www.allparts.com/Locking-Tuners-Vintage-3x3-Nickel-p/tk-0735-001.htm

Of course, you have to take measurements for the screws
and figure out pole height.

Are the shafts slotted?