Got a new Vacuum pump, cleaned up the CDR and hoses, etc. today. My problem? I cannot get the new pump (or the old one, for that matter) to fall into place where it is supposed to go. It came out easy enuf, but cant get the new one in. New pump has fifteen teeth like the old one. Never had this much trouble putting a distributor back into a gas engine before. What am I missing here?

Check down in the hole of the block, there's a 5/16" hex-shaped oil pump drive shaft. It mates to the hex hole in the vacuum pump drive gear. The shaft should turn and go up into the drive gear as you set the vacuum pump down in the block. It it won't lineup, you can turn it with a 5/16 socket and extension. Be sure to tape or otherwise attach the socket to the extension. If the socket comes off, it goes down in the engine! Try turning the hex shaft a little, the vacuum pump should drop in. Be sure to lube the o-ring on the pump. LOL, Fred

Thanks Fred,

Your suggestion, and a little more cursing, and a few more raps of my head on the bottom side of the hood did the trick.
The only thing I'll lose sleep over now is wondering...what O ring? Oh well, the old pump didnt have one either so I won't worry til I see huge puddles of oil under the truck tomorrow morning. Thanks again

Sorry, I lapsed back to the 5.7 Olds engine. Whoa!! Am I getting that old!! The 6.2 uses a gasket at the base just like any Chev engine. My apologies. By next year, I should be able to wrap my own Christmas presents and hide my own Easter eggs!!