You may know this already, but a good place to visit is Racecarsdirect.com
There you will find a section in 'Categories' pages of classic race car suspension and lots of uprights. You may spot some for sale the same as yours and so identify them?
!
Just had a look though the 7 pages on suspension, nothing like yours!
Also, a good info source is Dermot Healy
demothealy@btinternet.com
He has been trading race car parts for decades and my help you identify the uprights.