Looking for Alignment Advice

It drives straight as an arrow on good roads & seems to corner well, but when on roads that are not flat (truck grooves) it really sucks.

IMO this is affected by the tire. I've found the closer the tire shoulder is to a right angle, the more pronounced this is. I've heard the effect called nibble. A tire with a more rounded shoulder is less likely to exhibit nibble.

The specs I think that I'll have them shoot for are:

Caster: Left +4, Right +4.25
Camber: Left & Right -.25
Toe-In: 1/16"

This is what I shot for on the 73 Dart. The chassis would only give my alignment guy +2ยบ. I took it. Combined with the front end re-build it has sharpened turn-in and raised steering effort considerably. At road speed the power steering is still light on feedback, but it goes where it's pointed NOW.

As for being a bugger to align, the A-body caster/camber is set by rotating eccentric washers at the front and rear of the UCA. It is possible to chase a setting from front to rear and vice versa. It can be frustrating. Most shops are used to being able to add/remove shims to get the job done. It is a more straightforward process.