I recently went through this trying to find a set of Hooker headers for my 1990 chevy silverado. All the part numbers for that particular year don't come up any more.
The guy on the phone at Holley (who owns Hooker) was great. He said it's all due to the new EPA rules and government crackdowns on this mess.
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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