A playable vintage instrument is more valuable than a non-playable vintage instrument. Both are still vintage instruments. My new Martin 1T came standard with Pegheds. Replacing components of older instruments with more functional ones is very common. There is one problem with the Pegheds you should be aware of: they are threaded into the headstock. This is a potential hazard when installing them in a vintage headstock. The headstock may need rebored, and or the Pegheds epoxied into the headstock. If the old friction pegs are NFG replace them with functional tuners.
thread drift: I have seen vintage Fairbanks Banjos which were originally equipped with friction pegs, had fill marks from geared tuners on the headstock, and were equipped with modern planetary tuners. The asking and selling prices were very high. A vintage instrument that plays well is of more value than a playable vintage instrument.
Saw your second post. If you have authentic whittled fiddle tuners try using fiddle rosin on them to improve the tuning characteristics. Previous comments are still valid. What year Martin are we talking about here?
http://home.provide.net/~cfh/martin_ukes.html