I noticed something was weird when I took off the air filter. Turns out they used a single offset air filter base, filled the original holes and then drilled new holes to make it a double offset base like the MK2s, except they did not center up the base with the carb. The carb was about 30% restricted on my first test ride. Kinda like riding with the choke part on. The Case diesel water separator air filter is the same as the MK2 and MK3 filters. I stuck on a correct MK3 base, a paper air filter, filter clips and Wacker tamper cover for subsequent rides and pressure washings.
The cover is marked WEST BEND and is dimensionally the same as later covers. I will put it back on when the bike is closer to getting finished. Not sure if I want to use the Case filter. Flow bench testing many years ago showed a big air flow loss compared to any other filter. The base attaching screws are drilled for safety wire but none was used. I did use safety wire when I put the base back on.