Rear leaf's to coil's, and 6 lug to 5 lug - what year was the changeover?

[Russ.W.]

Few question for you good folks, if you don't mind.

Specific to 67-72 C10 2wd shortbeds, I'm trying to find out when rear coil suspension become an option over leaf's, and in which year became standard?

Same question for 6 lug to 5 lug changeover.

I'm considering ordering a complete rear-end housing from Moser.

Their website lists two options for our trucks:

- 1963-69 Chevy C10 Pick Up Truck
- 1970-72 Chevy C10 Pick Up Truck

They offer no option of suspension type (leaf or coil), nor lug count (5 or 6).

Does this mean rear coils weren't introduced until 1970?