On a small block chev (a 4.3 is a 350 with 2 cylinders chopped off) 40+ psi is considered normal at 3500 rpm. At idle, I often see 10-15 psi hot which is also normal. High milage units may be a little lower again, but still not a problem. Small block Chevs have an incredibly well designed and efficient lubrication system and it is rare to see problems lube related unless the oil isn't changed for long periods and sludges up.
On the other side of the coin, if the oil pressure is too high (especially when cold and a 50-60W oil) it can shear the oil pump and/or strip the cam gear. So more is not always better on this occasion!

This is why you need to warm the motor up some before blasting away from the dock on full throttle.
My bet is the oil pressure sender has died or the wire has come off it...