1970 Chevelle BR coded radiator

[Mr70]

To help you in your search Ray,those were the same 3 core Harrison side tanks used on certain "B" coded 1970 Big Block Auto trans. Chevelle-Elcamino-Monte Carlos when equipped with LS-3,L-34,LS-5,L-78,LS-6 engines.{BC-BJ-BK-BR-BW}.And also the same Passenger side tank used on the heavy duty 4 core Auto trans.equipped PD coded L-34,LS-5,L-78,LS-6 too.
The center cooling cores convolutions were what differentiated them,but you'll probably have that recored anyway to be more dependable for weekly driving,and should.

I don't know how original you want to be,but The Parts Place has reproduced most all these Radiator ID tags today.They are not 100% correct to the originals and can be detected from 10 feet away,but are close.