Firm Feel forges their own bars in house. PST has them made in large batches by a forge. Firm Feel also makes a bunch of different diameter bars, while PST only makes the 1.03's for A bodies. So it's mostly just a manufacturing thing, PST benefits in the cost department from running a larger manufacturing run of the same size bars. There are probably other factors, but I bet that makes most of the difference.
And if you don't want to be "pounded to death", don't run the KYB's with any of the larger bars. You won't be happy. No real reason to upgrade the LCA's beyond changing the bushings and welding on a stiffening plate, I have the tubular LCA's from QA1 and the benefits are pretty minor. You can skip the tubular UCA's too depending on your planned use of the car, the Moog K7103 offset bushings will get you enough caster for a street car if you're keeping the 15" rims and tires. Especially with the 16:1 manual steering, you probably don't want to run a whole lot of positive caster as it will further increase your steering effort. You can definitely run more, I run almost +7* of caster with a 16:1 box, but I do a lot of things that most people that drive these cars don't like.