You didn't say where you are, so I don't know what kind of parts deals you can get. Here in central Florida we can get a reground crank with bearings from Central Auto Parts for $89 exchange. You'll also want to replace the oil pump while you're at it...

Before you go to all that trouble, though, your immediate problem (low pressure) may just be a symptom of a worn out oil pump. Chevy engines use a gearotor style pump. They are very reliable, but if they get too much wear between the gears and, more importantly, too much wear in the pump housing on the top and bottom of the gears, pressure drops proportionately.

You might gain some oil pressure in the short term by changing your oil to Kendall Nitro-70 racing oil. I used to run it in my stock cars because those engines were built with extra bearing clearance and the 70 weight oil helped keep the pressure up. If you live in a cold climate, though, you're going to have a problem starting that engine when the outside temp drops below about 40 degrees.

If you have the time and are willing to expend the effort, drop the pan and change the oil pump. If this solves your problem; great! If not, then the problem is worn bearings / crank journals and you will have to go for the replacement crank. You won't lose anything except your labor because if you end up having to do the crank replacement you should change the oil pump, too, and you will already have it.

There is much debate about whether a standard or high-volume pump should be used in a stock engine, but whichever you choose you can boost the pressure output by shimming the relief-valve spring. The stock spring is set to regulate at 35 lbs. If you put a .050" shim behind the spring you should get about 40 - 45 psi.