If you ask me which 335 mod is the most frequently seen, I’d have to say tuner changes. In the mid to late 60′s, it was almost mandatory to put a set of Grovers on your Kluson equipped Gibson guitar . We all knew that Gibsons went out of tune too easily and most of us thought that it must be the somewhat pedestrian Kluson tuners. After all, even Gibson used Grover tuners on the top of the line 355 until 1964 so perhaps they knew something. Most of us know by now that it wasn’t the tuners knocking these guitars out of tune but a poorly cut nut. Usually, the upper strings stick in the slots and go sharp when you bend them. If the tuners were slipping, the strings would go flat. It took me years to figure this out. I changed the tuners on my 68 SG (back in 68) to Grovers for that very reason. A certain Mr. Clapton had a set of gold patent pending Grovers on his 335 and, considering the number of 335′s that have had these tuners, I would say it was all the rage back then. Then the 70′s brought Schallers which on the plus side are perfectly good tuners but on the minus side, are heavy and ugly and required more holes. At least with a set of Grovers, you could use the existing bottom hole from the Klusons and only have to enlarge the shaft hole. But the damage was done, as they say and now we have to deal with it. My initial thought, with a set of Grovers, is to leave them be. They are good tuners and they look OK. A Grovered Gibson will be a perfectly serviceable guitar but the purist collectors will always discount them (or turn up their collective noses at them). Put a set of Klusons back on with a good set of adaptor bushings-the ones that are “invisible” because the size of the part of the bushing that shows is the same as the real ones and you’re back to collector grade. Sort of. The shaft holes will always be bigger and you can’t hide that (and you shouldn’t). You can repair them but the guitar will always have an issue.
So, how do you price an otherwise collector grade guitar that’s been Groverized. Or Schallerized. Or perhaps Sperzelized. well, it depends on the guitar. You might knock $4000 or more off a $40,000 ’59 but on a 66 ES-335, it might only be $1000. It also depends on how clean the front of the headstock is. Most folks seemed to think you had to tighten down the bushings until the headstock dented. Those marks won’t go away and they diminish the original look. Knock off a few more bucks. Schallers leave an extra hole that will peek out the sides of a set of Klusons. Knock off another few bucks. There really aren’t any rules and that’s what can make buying any vintage guitar a tricky business. My approach is to look at the whole guitar. If, for example, it’s a player grade guitar with changed parts, Bigsby holes and perhaps some player wear, then don’t worry about the Grovers. It’ll be priced in. But if the guitar approaches mint condition with the only issue being the Grovers, then you may be paying a serious premium (for a mint 335) but ending up with a guitar that will always be a cut below an all original one-even one in way worse condition. As I’m fond of saying. Fifty years is a long time for anything to remain unmolested. If the only issue is a set of Grovers and the price is right, then I say go for it. You could find a lot of worse mods than a cheap tuner swapped for a better one.