For the record, the inline tach filter that has to be bypassed on a gm to run a stock tachometer with the MSD 6AL box is mounted on the intake of cars that came stock with an HEI distributor and is mounted on the back of the engine block on later models that had a computer controlled distributor. On my '86 IROC Z28, which came factory with a computer controlled distributor, it's mounted on the back of the block; even though I'm now running an HEI distributor. Man, I've researched parts on 60 year old aircraft that were not this hard to locate.