does a 1988 chevrolet silverado 5.7 only have one 02 sensor on the drivers side manifold

I do believe there is only one on this truck, but look around. I have seen up to as many as 3 or 4 on some vehicles. 1 on each exhaust manifold, 1 before the cat and 1 after. But I'm pretty sure the 88 Silverado has one sensor.

It might depend on if it has a dual exhaust or not. A factory dual exhaust would need at least two sensors.

I have a 1989 GMC C1500 and it has the one sensor but I did notice in the back near the firewall, it appears to have another wire for a second sensor but nothing plugged up to it. A standard provision for the factory dual that was mentioned maybe?

There is only 1 sensor on it

would a 3" maniflod fix a 88 1500 chevy pick up it used to have 2" maniflod