I won't spend any time with the background on the Kalamazoo Model 1. It's all available at Miles O'Neal's Kalamazoo Field Guide. Here's what I did to improve our Model 1 and why:
I added a power input module. This includes an EMI/RFI filter, and moves the power switch to the back panel, and off of the tone potentiometer. The original front-panel fuse and neon remain.
Volume and tone potentiometers were replaced; they had been abused and had intermittent open circuits at certain points of their travel, which made some nice high frequency squeals.
All resistors were replaced (with metal film) to reduce noise. All values were kept the same, with the exception of the 6BQ5's cathode bias. I measured the old one at 160Ω (schematic shows 150Ω) so I put in a new one at 160Ω... I had to keep some "mojo".
Terminal blocks were added & replaced to make it possible to use modern passive components (which have shorter leads than the originals).
Wiring was replaced to improve layout and grounding and reduce hum. (Original even had signal ground returns through grounded heater wires!)
The original multisection filter capacitior was replaced with new electrolytics on a new power supply turretboard that also holds the dropping resistors and a heater elevation voltage divider to reduce hum. An additional LC filter stage was added on the power supply, using a Weber 9H/120Ω choke.
Shielding was added on the cabinet, using copper foil tape from Stewart MacDonald.
Input input jacks were replaced with new from Neutrik.
No major cosmetic work was done. Just glued down some loose tolex.