Attempting to make a sleeper

So here is the deal, I’ve got a 2000 Lincoln Town Car and my goal is to make a sleeper out of this car. My intent is to keep the 4.6 in there and get as much power as possible from it, I know it’s not going to push 600 hp or anything like it. I’ve heard and read hundreds of people’s opinions and I know it’ll require a lot if I do keep the 4.6 but it’s worth a try. I’m also open to different possibilities like a 5.0 or something along the lines but I wish to stick to the 4.6. And I know there are those people out there that think I’m stupid and find it dumb, my buddies give me enough crap about it. The thing is practically a land yacht and weighs 4,000 lbs and I know there are better cars that you can make sleepers out of but I want to see what can be done with her. So what are your opinions on what can be done?