RD54s are Maxtor2190s 159mb 1224 cyl, 15 heads.  You
can substitute
 other MFM dives if you can find the formatter (or a MV2000 to use as
 formatter).  VMS is fairly tolerent of different drives, NetBSD does too.
 
Ok.  I seem to recall having a diagnostic on TK50 that's got a formatter on
it..
  RX55?  do you mean RX50 (dual 5.25 SSDD 96tpi) or RX33
(5.25 teac
 fd55GFV that does both RC50 and 1.2mb RX33)? 
It's an RX50.  It's been a LONG time since I've used this system. :)
g.