Also, only the AAZ pump from 1995 and over will have camplate that fit 10mm tdi head.
yes.... you can use 1.9td spring and shims.use:hydraulic head... that's it. The head is only complete if you use the collar, plunger and head. You can't mix the pieces. Even between to 10mm head, you can't interchange the collar or plunger.You might want to install a 1.6td regulator and adjust it so that timing advance will be ok for all RPM.
Why cant you interchange between 2 10mm plungers and collars?