My Toxic '74 Duster
Welcome!
Sounds like a great build you have in the works. Love cars that are built to be driven, after all, if you're not driving it, what's the point anyway?
Your chassis stiffening plan is good, US Cartool has great parts and the level 2 system takes care of all the major needs. As far as making your own stuff, I have done it both ways. On my Duster I made my own subframe connectors and sourced a tubular radiator support and J bars locally and combined that with US Cartool torque boxes. On my '71 GT I used the level 2 USCT kit. I really like the inner fender braces from USCT, they'll do a great job without being super obvious (like the J bars). I did NOT like their subrame connectors, but I installed them with the car up on jackstands. If I had to install another set it would have to be on a lift or rotisserie, the amount of welding required for the USCT subframes is pretty miserable, since you're doing it upside and with low clearance. I installed Hotchkis subframes on my Challenger, like all Hotchkis parts they're well thought out, fit well and have great instructions. And are really expensive for what they actually are.
The stock K frame also benefits greatly from some gusseting and seam welding. You can buy the reinforcement kit from Firm Feel, or you can make your own. The biggest areas to gusset are the LCA pivot holes and the steering box mount.
For handling there are a lot of ways to go, it really depends on how competitive you want to be and what your budget is. The biggest decision is what wheels/tires you want to run. If you're married to 15" rims then the level of handling you can achieve is significantly limited by the tires available. BFG T/A's and Cooper Cobra's look cool, but they're hockey pucks compared to modern tires. If you go up to 18" wheels you can run much wider and better tires. I have 275's on the front of my Duster with 18x9's and 295's out back on 18x10's, and the 200 treadwear Falken Azenis I run have incredible grip.
If you're going whole hog for street handling and autoX, "the list" looks something like this. Sure, you can buy a Hotchkis TVS but you get some stuff you don't really need, a few things you probably don't want (heim joints at the UCA's), and you don't get other stuff you do need. Bergman Autocraft's current kit is a better match, although the new SPC UCA's are
really expensive. I'm sure they're amazing too but the Gen I SPC's are awesome too. This is just the front suspension, I still have leaf springs on my car but the AFCO's I run are discontinued. Basically you pick a set of leaf springs you don't hate and run them with a Hotchkis or Hellwig sway bar and whatever shocks match the front. I have spring sliders on my car, they're nice but not necessary.
This is basically everything on my Duster at the moment. A couple of the brands are different. Not all of this is necessary for a good handling street car, if you're not lowering the crap out of the car then you don't really need the QA1 LCA's, you can just box the stock LCA's. RCD Bilsteins are great shocks too, you can substitute a set of 1.08" torsion bars from BAC for a less firm ride, that sort of thing.
QA1 Adjustable strut bars
1974 DODGE DART QA1 52311 QA1 Dynamic Adjustable Strut Bars | Summit Racing
QA1 LCA’s
1974 DODGE DART QA1 52307 QA1 Mopar Control Arms | Summit Racing
QA1 tie rod sleeves
1974 DODGE DART QA1 52325 QA1 Heavy-Duty Tie Rod Sleeves | Summit Racing
Proforged tie rod ends-
1974 DODGE DART Proforged Chassis Parts 104-10157 Proforged Tie Rod Ends | Summit Racing
1974 DODGE DART Proforged Chassis Parts 104-10156 Proforged Tie Rod Ends | Summit Racing
Proforged lower ball joint (driver)
1974 DODGE DART Proforged Chassis Parts 101-10129 Proforged Ball Joints | Summit Racing
Proforged lower ball joint (passenger)
1974 DODGE DART Proforged Chassis Parts 101-10128 Proforged Ball Joints | Summit Racing
Hotchkis 1.5 shocks (non adjustable, just the front )
1974 DODGE DART Hotchkis Sport Suspension 70020013 Hotchkis Sport Suspension 1.5 Street Performance Series Shocks | Summit Racing
Proforged ball joints- x2
1974 DODGE DART Proforged Chassis Parts 101-10126 Proforged Ball Joints | Summit Racing
PST manual steering box
https://p-s-t.com/i-23161668-manual-steering-box-16-1.html#!year=1974||make=DODGE||model=DART
Moog pitman arm (manual)
1974 DODGE DART Proforged Chassis Parts 103-10015 Proforged Pitman Arms | Summit Racing
Moog idler -
1974 DODGE DART Moog Chassis Parts K7086 Moog Replacement Idler Arms | Summit Racing
Hellwig 55905 front sway bar-
1974 DODGE DART Hellwig 55905 Hellwig Motorsports Tubular Sway Bars | Summit Racing
Bergman Autocraft SPC UCA’s (1st gen)
BAC SPC Upper Control Arms - Bergman Auto Craft
BAC Delrin LCA bushings
BAC Delrin Lower Control Arm Bushings - Bergman Auto Craft
Firm Feel 1.12” bars-
Firmfeel Mopar Suspension and Steering
Firm Feel greasable LCA pins
Firmfeel Mopar Suspension and Steering
Or add power steering-
Borgeson box from BAC
Borgeson Steering Box Kit Large Sector - Bergman Auto Craft
The full build for my '74 Duster is here
My "new" '74 Duster- or why I need a project like a hole in the head, it's still very much a work in progress although I do basically use it as a daily driver.