Here is a NOS EGR valve for the big block LS4 which was used in 73 -74 and may be other years part no is 7049867 any questions call me at 410-320-7018
If non-California (engine suffix code "CWR"
original valve was GM #7049867. This valve was discontinued and replaced by GM #17051872 and the latter was discontinued without supercession in 1987.
http://www.ebay.com/itm/NOS-73-74-LS4-GM...me=STRK:MESE:IT
160.00 free ride here