Hi all, I have two remaining HD FDD kits to suit STs and Megas. (Not STE)
Both are premodified new Sony MPF920 drives (disk swap detect, and DS0), and the small 74LS151 based HD pcb that needs soldering in to make it all work.
I can supply a modified rom chip too to let your ST run the HD mod without a 'driver'.
(Just advise your TOS version and we'll work it out)
Comes with instructions that are generally suitable for most ST models.
$A35 including postage.
A few members here have bought one, and the results speak for themselves.
I can build more if required. PM me or email if you want one. (I can also supply Lascan or autoswitching 16Mhz Overclock generator boards too... just have to make some if required)