will led lights work in my 1975 class C?

Yes they will... to a point.

You'll need to get RED Led's for the RED Lenses and YELLOW Led's for the YELLOW Lenses. You should NOT install white led's lamps in these places.

The amp load to make an Led turn on a signal light might be too low to allow the signals to "load down" so it's possible you might need a Led type turn signal flasher.

The Cruise Control might not disengage because the brake lamp interrupt might not have enough amps to trip out the cruise unit.

I put these in my OEM tail lamp housings with original lenses. It is like having new (RED not pink or purple) vivid tail lamps.---------- PRODUCT INFORMATION from superbrightleds.com----------

Qty | Product / Options |
4 | 1157-x12-DI: 12-LED BAY15D bulb | $ 4.99 |
1157-R12-DI: 1157 Red 18 Degree

I put these in the side wall patio lamp fixtures and covered them w new amber lenses in hopes of attracting fewer bugs:
http://www.ebay.com/itm/ws/eBa...US:1123#ht_724wt_936