No it is not a hard job at all.
It only needs balancing it one of the wheels are changed.
If the turbo only needs bearings and seals then as long as the turbine shaft and comp wheel are marked up and replaced in the same place then no balancing is needed.
I can get every part for the CT26 and CT26 small as the CT20b should be called.
The comp wheel is bigger on the CT20b but the turbine wheel is smaller than the CT26. I feel the best match would be a CT20b comp wheel on a CT26.
Bob
Designer for turbo set ups on F1 cars, and Nitrous Oxide Systems of the USA in the 80s