[Mr70]

Not referring to this particular ebay auction discussed here.
This air cleaner style can be homemade by using other air cleaners parts also.I used to have a single snorkle,same length as the dual,that worked very well to make a dual.I stamped "HOMEMADE" on the inside bottom of it,then sold it as a homemade unit for $100.00,& still see some out there today.It is pretty easy to tell if they were homemade.All its parts can be found to make,although they will look homemade,but some don't care,& are honest about that.
As far as the 1970 L78 Chevelle using them,I have never seen that.It was built to early in the model year,then cancelled before the dual snorkle design was released.The Dual snorkle code for the Chevelles was CO on the buildsheet.I would like to see a 1970 Chevelle L78 Buildsheet reflecting that,it if anyone has one.
The LS6 Chevelle was a later produced RPO,& received the dual snorkle sometimes,starting in Spring of 70.
I believe this Dual snorkle design was produced & slated for the Newly designed 1970 Corvette,with the LS6 engine option.Not having anything to do with carburetor noise issues with other cars.This also was why the new low aluminum intake was designed,because of the new 1970 Corvettes BB hood to engine clearance.
The 1970 Corvette RPO LS6 never fruitioned,so the factory used up the already produced Dual Snorkle inventory on the remaining low rise Aluminum intake later built LS6 Chevelles,L78 Camaros,& L78 Novas when possible.