Help with identifying GM P/N's

[69L78]

Can someone help identify these GM part number's and know the year when these numbers would have superceded?

[Mr70]

They're sidepipes w/mufflers for a 1969 Corvette w/427cid. w/side mounted exhaust.
#3979480 is R/H,and replaced the original assembly line pipe,#3949184 on July,1970.
#3973871 is L/H,and replaced the original assembly line pipe,#3949183 on April,1970.

[69L78]

Thanks Rick