Hi, I have a Dana 44 with front discs and wanted to upgrade to Wilwood discs all around. The instructions say these fit 66-75 drum brake spindles. How do I tell if I have the original drum brake hubs and spindles?

If you have a disc conversion already, the drum spindles and hubs are likely long gone. They are not used in the common disc conversions, and not interchangeable. To run the Wilwood kit, you WILL need to have the correct recommended parts from the stock drum setup. If you do not have them, you will need to find them good used, as they are not currently available new. With a GM disc kit, we do have part # 3024, a Wilwood caliper set, which may replace your current calipers and be an easier upgrade.