Shown in the pic below is the engine port I'm referring to behind the manifold. Just had the motor redone and I am unsure of what went here as it was disassembled about 6 months ago. Its a 350 Vortec TBI.

It may have been plugged and removed by the machine shop when the block was cleaned?

 

Oil pressure sending unit

Make sure something is in there when you start it up; otherwise .... I don't know how far from the source you have ever seen everything coated with oil, but I can promise you, you'll have one you can tell your grandkids about right there. Fortunately it'll be over with quick as there's only 5 quarts or whatever to begin with.

Note that there is another plug place just to the left of that in that pic, right where the pass side head and the intake manifold meet; needs a plug there. Same result if it's missing, I think oil can probably shoot about 30 feet but I could be underestimating.

 

Okay thanks. My sending unit is right above the oil filter itself, so I can just plug this?

 

Yup.

I'd suspect you could render about a quarter acre of lawn temporarily permanently infertile, before you could shut it down, if you don't.