performance for the '84 500 SEC
 

So what are a few things that I can do to improve daily driving performance and possibly see some small hp/tq gains with my 1984 500 SEC?

There are several things that can be done to help. Since the fuel computer controls the fuel mixture at all times except full throttle, adjusting the fuel control pressure slightly lower. Also by advancing the timing 4-5 deg after the fuel pressure adjustment.

OF course the best way to gain 40HP is to install a 560 engine.

So say I want to drop in a 5.6L. Is it a direct fit in place of the 5.0 with just a 5.6L crossmember or are there other modifications? Can I retain the 5.0 transmission?

Other than the intake & exhaust manifolds the engine is a direct bolt-in!

is there a nice set of headers that would fit my application? also, how much can a 5.6L be had for?

You can get a custom set of headers for $1,500. A supercharger kit for a 560 SEC starts at $1,500. Boost and hp are dependant on you and what additional power adders you go with on your kit. You will need to buy your own Procharger P1SC.

At 7 psi my car dynoed at 346 RWHP and 404 RWTQ with no intercooler but I did have a methanol/water injection kit. I'm having some custom pulleys made, cog and 8 rib, now that should take me to around 10 to 14 psi and well over 400 RWHP not to mention that I'm now running a large air to air intercooler.