The middle setting on the Volvo 270 is usually a good all around setting for an 18. the lower setting puts the bow down too far. Upper can be faster, but I found better handling in the middle.
A port helm boat should typically have a left hand prop. You can change the rotation of the drive easily.
The older volvo drives generally have alot of steering torque at the wheel. Power steering or hydraulic steering is generally the only way to get rid of it.
What size prop do you have now. Griz can set you up with a nice one for your boat.
1978 X-18, SBC, Volvo 280T
Big Grizzly 21 Solas Prop
Heart Bay, Lake George, NY