Can someone ID this part for me?

If you are standing in front of the car facing the windsheid This little unit screws in to the top of the engine right next to the distrubiter on the right side and it is oilly and has a wire connecter that conects to it. almost looks like some kind of vacum valve I tried to take it off and broke it

yes it is one wire going to it

Yep, oil pressure sender.  Early cars have a small capilliary line going to the gauge on the dash, yours obviously has the electric gauges.

I think you guys are right now I have to find out where to get one. broke the thread trying to take it off

Did you manage to get the entire thing off of the engine?  Not sure if the 80 sending unit is the same as the 82 but probably so.  if the large hex shaped part is what broke, its plastic anyway but filled with oil and messy.  If you will reach under the large base with a 9/16 wrench you will be able to unscrew the sender from the engine.  I custom made a "Bubba Wrench",  bent into a kinda square cornered C to get mine out.  They are notorious for leaking down on the back of the engine and transmission.  Replacent should be available at any auto parts store or your local GM parts counter.

Just picked one up for the '78 today. Chevy dealer wanted a whole lot of money. Napa was a lot less. Advanced Auto Parts was less than 1/2 Napa's price. Ordered last night from Advance and it was at the local store first thing this morning. Haven't changed it yet, but I assume it's the right one and will be ok. Advance is a Carlisle Event sponser too.

Damn, these guys are good. I would need at least a sketch on a napkin but preferrably a picture. And then I would say that it is the dew hickey that sends a signal to your whatchamacallit.

   And don't forget to check the blinker fluid.......