All good suggestions above, from a group of folks who would not steer you wrong. Having said that, you must stay true to your wants. You said that the only thing for sure that you know you want to do to the car is an LS swap. That would be my first step if I were you. Sure, it's gonna eat up $10K, but that leaves you $15K to make the car handle better, and have a more modern interior.
You don't need an aftermarket subframe, or a 4 link rear, to have a cool looking, nor a great handling car. Your not gonna track this vert, so don't bother trying to build a race car. Very few track capable builds actually get tracked. Don't waste your money on the high end suspension items. Go with some nice control arms, maybe a kit from RideTech, with matching shocks, and match the rear stuff to the front suspension...done. Mini tubbing just plain looks mean with the huge rear tires, but the wheels and tires to get that look (and tire patch, which leads to better handling when balanced) will eat up a large sum of what you have left after the engine swap.
It's your car, and only you can make the decision based on what your wanting. Stay honest with yourself, throughout the build. Don't start a full blow apart rotisserie build, if your not completely sure that you can financially handle the ENTIRE endeavor, and have the patience to wait it out. I get tired of seeing people sell off unfinished projects because they ran out of money, and patience. If you can do a lot of this yourself, you'll save tens of thousands of dollars.
Shop for bargains. That's what I did. I never bought one single item of my build on a whim. I waited for a deal, and jumped on it. I've had my car apart for just over four years now, but I'm down to just a few more interior items, and a stereo install. I knew what I wanted then, and I kept true to my vision that I had the entire time. Make a spreadsheet with your budget, YES GUYS I SAID BUDGET, and work it out. It's doable for $25k. Check out this DEAL that just popped up, for instance...
http://www.pro-touring.com/archive/i.../t-118390.html