FirmFeel is a good vendor. I think your stock pitman and idler arm may do for now. With a $1500 budget it wouldn't be too difficult to improve your handling; however, odds are you won't be getting wheels and tires with that budget. What rear end do you have in the car? A 7 1/4 may not hold up.
If it were me, I'd most likely do these upgrades
1) Front end rebuild: Replace all of the steering and suspension components utilizing FirmFeel or Moog (found on rockauto) parts. I'd most likely install the Moog offset UCA bushings. If you want adjustable strut and tie rods you'll either have to go with FirmFeel or Hotchkis.
2) New 1.00" or greater T bars: I don't recall how expensive PST's bars are but I believe they were cheaper. Plus they have a 5-10% discount for FABO members. If you want a larger size than what PST offers (like I did) I'd definitely go with FirmFeel. Unfortunately, I don't know much about leaf springs to help you out. I bought the TVS which had a set of leafs picked out for my system already.
3) Front disc brakes: It depends if you want bbp or sbp. I see lots of KH setups for sale here for $200-300; however, most of them are cores. Odds are bearings, seals, rotors, studs, pads and sometimes even calipers have to be replaced. Overall it can be very expensive (I did it). If you're still looking to go the sbp route Scarebird offers a cheap DIY kit utilizing off the shelf components. If you go bbp you're going to want some 73+ A body or FMJ spindles. You'll need the larger ball joint upper control arm which you could probably find used here or just order a tubular one. Hotchkis, I believe, added some extra geometry to their arms that make them a little more superior to the others; however, they're the most expensive. My other options would be FirmFeel or RMS for tubular UCA's. As far as the brakes go for the bbp, I'm not too familiar with the factory setups on many cars. Doctor Diff offers some brake kits utilizing a 10.7" rotor or an 11.75" rotor. I think Wilwood may have a good setup as well for either bolt pattern.
4) Steering box: FirmFeel offers a rebuild kit for the steering box or you can purchase a new one and send yours in as a core.
5) Sway Bars: For now I'd start with just the fronts. Hellwig has an adjustable, hollow front sway bar. FirmFeel's are non adjustable.
6) Shocks: I'd say go Bilstein RCD's or Hotchkis's Fox shocks. I've got Bilsteins and it was a huge improvement in ride handling; however, the Fox shocks are more improved for a pro-touring type car. The Bilstein's are at $400 and I'm not quite sure how much the Fox shocks are, but I believe it's somewhere around the $600 range.
7) Wheels and Tires: Wheels and tires are tough for Mopars (as I've been finding out) the center register is pretty big for most aftermarket wheel so be sure to measure. If you go with sbp hubs your only real options for 17" wheels are Coy's or Motech Performance. They're probably the cheapest wheels you'll find and are offered in both bolt patterns. Unfortunately, even with these wheels and a good set of tires you're looking at at least $1k out the door. However, neither are setup to allow you to have a wide tire underneath your car. I'd say no more than a 225/45/17 for the front (with slight modifications) and a 245/45/17 for the rears (with an A-body rear end). Now if you go bbp, your options widen up. 8 1/4 rear ends are good as they're usually bbp and you can pull the brakes off a Jeep Cherokee, I believe. 8 3/4's are quite more expensive (I've got almost $2k in mine but I replaced every single part on it). If I were to do it again, I would have started with a B body rear instead of an A. The B body rear better matches the front when it comes to offset. There's also not as much room you think there is under the wheel tubs of A bodies (as I also figured out)
Now, looking into the $1500 budget, the things I'd probably put on priority would be the Front end rebuild, new T bars, rebuilding the manual steering box, getting a Hellwig front sway bar, and purchasing some Bilstein RCD's (maybe some Fox shocks if you can afford it). I think you're going to have to hold off on wheels and tires for another day. This is if you have front disc brakes, if not, I'd probably ditch the manual steering box upgrade and sway bar and focus on those.