Any idea on the size or tuning ratio? I can't seem to find specs on them.
A lot of people on the Squier '51 modders forum like these from Stew Mac, along with the requisite bushings:
http://www.stewmac.com/shop/Tuners/G...6-In-Line.html
http://www.stewmac.com/shop/Tuners/T..._Bushings.html
At least with these, I'd know that the tuners/bushings will work for sure with the '51, although I'd have to drill for the set screws. I kind of like the vintage tuner thing where you stick the end of the string in the post and twist from there. My bass tuners are like that.