I just tried this from a hunch while I barely understand electric circuits.
Bum fuzz was made after B&M fuzz. it came from Tonebender Jumbo, and Jumbo came from Big muff. and they are not far from Tonebender MK3. it means this pedal would work with Germanium transistors.
Sola Sound make 3 different versions of Bum Fuzz units with BC184, BC549C, and ZTX109. BC184 and ZTX109 versions look same to each other except ZTX109 version comes with better and older electric components. BC549C comes with cheap ass version. and, it has 3 of different resistors and 2 of electrolytic capacitors at least. I replaced them with 33k, 100, and 100k resistors an 2 of 0.1uf fixed caps.
OC139, OC140, OC141 are NPN germanium transistors for computers (yes, the computer) from late 60’s. They are period correct for late 60’s and early 70’s fuzz I guess. and, have the similar Hfe range as well. most of them I found on ebay.co.uk had 100 to 200 Hfe range. some are less than 100, and some of them are over 200.
It’s the shop I found ZTX109 and OC139 transistors
And, this pedal sounds great with OC139. I don’t see any reason to try a different setup anymore. this modified Germanium Bum fuzz unit has overdrive to medium or leather high gain fuzz range now. somewhat sounds like MK2 and feels like MK3.
It was like this a couple of months ago