Are suspension parts differernt for a V-8 K frame and the slant 6 K frame?

If you just want to do it in more manageable pieces, then first go over everything as suggested above and see where the 'scary' problem is coming from.

I did the kit approach when I first got into this and am hesitant to push anyone that way. The stiffer (poly) bushings are best for those really into sporty handling. Otherwise, my suggestion is buy good quality replacement parts from the parts store. Moog and a couple of others I'm blanking on are generally still decent quality and good fit. The Moog 'problem solvers' are useful if you can't get enough caster.

Wandering and following the road are often due to loose wheelbearings, tie rod ends and toe out.

I'm too am not a fan of staying with the /6 t-bars Unless you will be drag racing. If/when you go to buy your new t-bars, make sure they are clocked. They will be a right bar and a left bar. Firm Feel's and Chrysler bars are clocked, and maybe some of Just Suspensions. While I agree that anything up to 1.04" will be OK, unless your really looking for sporty handling, anything down to .93 will be good.

More important for a reducing roll and overall response to steering input is a front sway bar. Firm feel has come up with a decent solution for cars without swaybar tabs, and you can see what Hotchkis, Helwig or Just Suspension may have. Skip the addco IMO. Some of what you are paying for is the thought and planning that went into making a bolt up solution that is not mickey mouse. Sway bar bushings are a good place to use polyurethane. Only reason not do the front sway bar would be serious drag racing. (again all IMHO).

All of this assumes the tires are in decent shape. Include them in your check up.