The C3 runs with three CR123 batteries, and LiIons cells (2) can also work in C3. The voltage requirement for the C3 using P90 or P91 LA is essentially 9 volts. The B65 battery pack is make up of four 2/3A nimh batteries with a combined voltage of 4.8-5.6 volts or so, much to low to drive the LA's. If you could get the B65 pack to fit in the C3, via a battery extension, you could drive a KL3 or KL5.
Bill
Forgot to add that you could run the P60 LA, which you do doubt already know, as well as a BOG 3 watt led drop-in.
Bill
Bill