Hot rod timeline question- Z-ing a frame?

Anyone know when abouts guys started Z-ing frames? Did the hot rodder's get the idea from racecars of the era?

 

Back in the 1920's you could buy a bolt on kit for a Model T Ford, so I guess you could call speedster owners early rodders.

 

A bolt-on Z kit? Thats interesting.

 

It would be interesting to see a scan of that.

 

In Rodders Journal 22(pg. 10) there is a 1920 T that is Z'd in the back and it appears to be bolt on plates.