454 Oil Pressure

[76Charlie]

So my 350 had a nipple fitting into the block behind the intake manifold, which had a metal hose covered in rubber that led to a metal line through the fire wall. I thought this was a vaccum gauge and cut it(crap). So now my issue is how to set up oil pressure lines for mechanical oil pressure gauge in 76 GMC pick up? I don't know where to plug in at, how to run the line so it doesn't leak etc. Thanks in advance