With thanks to European Spotters and Kevin Dupuy, a rundown of the aircraft noted at Murrieta, CA on 08-Mar-2017.
285 - DHC-6-300 Vistaliner N190GC Grand Canyon Airlines (Monarch Enterprises LLC)
359 - DHC-6-300 N359AR Twin Otter International Inc.
406 - DHC-6-300 Vistaliner N171GC Grand Canyon Airlines (Cortez Fisher LLC)
470 - DHC-6-300 N805RT Ikhana Group Inc.
499 - DHC-6-300HG N808RT Ikhana Group Inc.
537 - DHC-6-300 N537AR Twin Otter International Inc.
697 - DHC-6-300 Vistaliner N178GC Grand Canyon Airlines (Cortez Fisher LLC)
The Grand Canyon aircraft are presumably undergoing Ikhana's "ReLife" program, as has previously been completed on at least two aircraft.
Storage compound near threshold of rwy 36:
40 - DHC-6-100 N902RT Ikhana Group Inc. (fuselage only, ex Westcoast Air c/s)
51 - DHC-6-100 N903RT Ikhana Group Inc. (fuselage only, ex Westcoast Air, c/s)
141 - DHC-6-200 N141PV (wreckage)
+ 3 or 4 other fuselages, which may include:
9 - DHC-6-100 N806RT (ex DQ-FEZ)
87 - DHC-6-100 N807RT (ex DQ-FEY)