Thanks to all.
The system now boots (at least partially) into VMS 5.1:
7..6..5..4..3..
Tests completed.
Loading system software.
2..1..0..
VAX/VMS Version V5.1 Major version id = 1 Minor version id = 0
..
PLEASE ENTER DATE AND TIME (DD-MMM-YYYY HH:MM)
PLEASE ENTER DATE AND TIME (DD-MMM-YYYY HH:MM) 04-MAR-2005 03:04
$! Copyright (c) 1988 Digital Equipment Corporation. All rights reserved.
The VAX/VMS system is now executing the system startup procedure.
%%%%%%%%%%% OPCOM 4-MAR-2005 03:06:19.27 %%%%%%%%%%%
Logfile has been initialized by operator _OPA0:
Logfile is SYS$SYSROOT:[SYSMGR]OPERATOR.LOG;762
%LICENSE-I-LOADED, DEC FORTRAN was successfully loaded with 50 units
Now all that remains is to get Quasijarus onto some TK50s so I can
run the One True UNIX.
Thanks again for your patient help!
John