I don't know about Los Angeles cars, but the BEST place to find a build sheet on a 1970 Hamtramck E body is behind the plastic bucket seat back on the drivers seat. I have found several there, and they are generally in the best condition.
I once bought a FJ6 T/A body, and pulled the back off the bucket seat and found a mint build sheet,
folded over twice in a square. It was almost like a brand new sheet of paper.
Greg
Wards Classic Car Radio Repair Specializing in restoration and sales of Mopar A B E body radios We can restore YOUR radio usually in less than 7 days Visit our NEW website.. http://www.wardsclassiccarradiorepair.comgregward@mchsi.comphone 256-852-0955
