I got similar seals from an AC hardware store and fixed them on the impy when the engine was out more than a year ago and they're holding very well. They were about $2 a piece, and they're a little bit smaller than stock. Only reason I got them is becuase the local dealer only sells them with the pipe and bolts for $115.

 

what kind of seal were they?

 

gm parts direct has the right seals for only $3.55 ea.i just bought four myself

 

Okay, I'm in the middle of a head swap right now so I can tell you with absolute certainty, (because I just measured one!), that those seals measure 1.100" O.D. and .450" I.D. They must be Metric, but these are the English (i.e. inch), dimensions. I found and almost identical washer/seal at AutoZone in their oil pan drain plug gasket kit, (which they keep behind the counter), and bought four(4) of them at 99 cents each! Total paid with Tax was like $4.20 for all four seals and yes, the local Chevy dealer here in Michigan wanted like $5.44/each for these things??? Try your local AutoZone for these things.