Steve:
As a test purchase, today I bought two LED bulbs at HOME DEPOT, made by Meridian, #13177 -- 7 watts with a C7 (candleabra) base. The fine print on the package says "Use in 120V Fixtures Only." Since the original Dept 56 wires & sockets were intended for 120V, but I applied the Dept 56 low-voltage distribution system to them, I believe these bulbs might work. And if not, the "test" only cost $5.
In case my test doesn't work, please provide the brand and source of your LED bulbs.
With thanks upfront,
Mike (ritrainguy)