Walter,
CA is tricky with twinscrew. You need a non commercial class A for it, with single rear (and trailer under 10000 lbs) the regular license should be ok.
IMHO forget the M2 106, limited to too small engines. With a M2 112 you could get a bigger engine, but when you are going used, use the CL's.
Look also for a jake brake and stay away from the exhaust brake. You will be much more relaxed going down Cajon
(or any other grade)
Thomas