Do you need a cdl to drive a 1979 Ford l7000?

I'm assuming this to be a single axle truck. Single axle trucks can be a bit ambiguous - if it's registered as a vehicle with a GVWR of 26,000 lbs. or less, then no, you don't need a CDL unless it's carrying hazardous materials or else is designed to transport more than 15 persons (including the driver). If, on the other hand, it's registered as a vehicle over 26,000 lbs. Gross Vehicle Weight Rating, then yes, you need a Class B CDL, minimum.

If it's a registered farm vehicle or motorhome, then it's exempt from CDL requirements. You need to check with your DMV to find out what the state's licencing requirements are for non-commercial vehicles of that weight class.