good suspension setup

Before even considering spring, shock, or sway bar changes, do this:

http://site.cobranda.com/tech/aarms.pdf

Personally I prefer a fairly stock suspension (good quality parts) with really, really good shocks - namely Konis.

The Konis are adjustable. You can make them stiff for ultimate handling or soft for a better ride.

IMO too many people go for all out handling with ultra stiff lowered springs, low aspect ratio tires and really stiff shocks. It corners like a go cart and rides like one also.

A big part of the ride on these cars came from the tall skinny tires and the long spring travel. Take those away and it will give you whiplash over bumps.

Also a good front end alignment with lots of positive caster will cure the "wandering" on the highway.

"Good suspension" is pretty subjective. My mother and teenage son would give two different descriptions.
Generic advice is replace worn parts, lower your UCAs, get a good alignment and stiffen the chassis (export, monty carlo and sfc). Convertibles are very weak. I can twist mine like a dog peeing on a fire hydrant when I push it and I do have a good suspension.

I don't know what kind of events you have down there, but if there are any classic Mustang/Ford open track events, you might check some of those out and talk to the car owners about their setups.

I love going to the Mid-America Shelby meet at Hallet and looking at some of the cars and talking to their owners. You can get great ideas and feedback on setups at places like that.