I have successfully aligned quite a few 5.25 drives.
Using a known good disk and a program on the host machine to keep the disk spinning (BBC micro diags), I put a scope on the head output and tweak the position (mechanically, but being careful not to move the stepper at all) until I get the maximum peak voltage on the wave form then step the heads back and forth and fine adjust as necessary to get the best readings across the disk.
One point, when the head on some drives, steps to track 0 and the detector switch is initiated, often they continue to step to a 0 phase position after the switch is actuated so you need to have the drive step to track 0 initially before you start adjusting as you can get it all reading perfectly then find when it resets the drive, its all out again.
Its actually quite fun. i have done Micropolis, TEAC, Mitsumi and Tandon drives by this method and got them all working.
8" I have never tried.