Honestly, for what you're wanting, torsion bars truly are the only way to go.
Trying to swap in a suspension from another car is going to result in a lot money and you're not gonna have the correct geometry. There's a lot more involved than simply cutting out from a crown vic and then welding it into an A body. The reason kits like HDK, Gerst, RMS cost what they do is in part due to the time and research and ultimately trial and error. I looked into building my own and cost in materials alone was going be over 1200 bucks.
For the purposes you've laid out, the best way is the Torion bars. Upgrade the control arms, shocks, bushings and even the bars and it'll handle just fine. You're not gonna have a rack and pinion but you can get a good steering box and be good enough.
I'm gonna tell you this, no matter which way you go, youre gonna be flirting with 2 grand or more, there's no way around it. Which is why I went GTS, because it was only a couple hundred more by the time I got done adding up th costs for stock replacement stuff and upgrades.