I don't think there are any definitive ways to track it down , short of tracing back to the original sale. I think that you can safely say (99%) built between 1970 & 1974 though.
The concert toms were also sold as separate item.. "The Eight Brothers"..
I do recall though that the build quality of these sets was A1.. and another recollection is that it would take me 4-5 hours to set up a kit out of the box.
Rest assured.. if you do track down the missing toms you will have a kit of decent value.. IMO.
After another search I found this link.. Where ??? right here under our bloody noses...
http://www.vintagedrumguide.com/images/my_collection/literature/pearl/1970-pearl-catalog-4.jpg
Cheers
John