There were both, in Brass, BUT if someone made a resin, or plastic example of either I'd buy! Expecialy the MK5000C/MK50-3, I want 2!!! I'd say find a company, like Kaslo, or a smaller, one or two person operation and suggest a Resin/plastic shell idea, the SD60MAC is SORT of simple, IIRC its a normal SD60M chassis, so the P2K chassis could be "reworked" or what have you?
The MK5000C is harder though...