Is it possible to get my 74 Duster slop free steering

Yeah well....I actually drive my old cars, it's the best part, sometimes to other states at the drop of a hat. Don't be offended but not everyone is out to set track records. :)
I set my 68 up years ago using Tom Condran's book as a guide and it's worked out well for ME. 73-76 K member and discs, .920 T-bars with 16:1 manual steering. Great feel as long as I'm not parking. UCA's have Moog offset bushings and I doubt they would adjust to 8* caster anyway.

Wow. So, you know that I don't "actually drive my car" how? You know what they say about assumptions.

My Duster is the newest model year car that I own, and my daily driver. I drive it about 10,000 miles a year, give or take. I commute to work in it, I get groceries in it, well, pretty much everything because it's either my Duster or my '71 Ford F100 4x4, those are my running vehicles at the moment. And yes, I put 10k miles a year on it with 1.12" torsion bars, 13" brakes from DoctorDiff, Hotchkis shocks, Helwig sway bars, and 16:1 manual steering with +6.5* of caster and 275/35/18 tires up front.

Tom Condran's book was great 19 years ago when it was published. I have it too, but you also have to remember that when that book was written the parts available to set up the suspension on these cars were extremely limited. A lot has happened since then- tires and wheel options are better, shock choices are MUCH better, more torsion bar sizes are available, there's a wide selection of tubular control arms, brakes, etc. Frankly, you can do a lot better with the parts available now than what was described in Tom's book. It's not that it isn't relevant, but it's pretty outdated with today's aftermarket parts. Even with the first version of updated suspension on my Challenger 10 years ago I was well above and beyond the recommendations in that book, and I put 70k street miles on that car.

You like how your car is set up, you "actually drive it", that's great. But +2* of caster is underwhelming, and even street cars benefit from more.