I suppose this is useless trivia, but according to the platter/head/cylinder layout (2/4/306) that MMI drive in your Hyperdrive is from a logical standpoint literally a shrunken clone of the Seagate (Shugart) ST-412, the full-height 5 1/4" drive used in the IBM 5160 XT. (and namesake of the "ST-412" nomenclature denoting ST-506 drives which support buffered seek requests.) Space issues aside if you had an XT sitting around you could literally uncable the drives from both machines, swap them, and format them to full capacity on each other's controllers using the stock settings.

(It's probably sad that I didn't have to look up the Seagate settings. I had them memorized from having an ST-412 as my first hard drive.)

Basically what this translates to is almost *any* MFM (or RLL, they're the same hardware, just the data encoding method differs) hard drive with four or more heads and of suitable physical size would work as a replacement for a bum Hyperdrive. Drives with fewer than 306 cylinders are pretty rare. (Of course, if the formatting software lets you specify the size/geometry than you could use basically any drive that fits.)