Dear OP,
I've ready through all of your threads, from "Which lowering springs" to comments "What front splitter is this?" This is not meant to flame you, but rather to give you some strong advice.
First, please create a build thread where you also tell us a little about yourself. What do you do for a living? Do you have a garage that you can work in? Tools? What is your level of mechanical skill? How many cars have you owned and modified in the past? What is your goal? If you're making $9 an hour and this is your first car, 99% of the people on here will tell you not to get into a motor swap because you'll be in way over your head. (I'm guessing DK might be the 1% that encourages you to do it as it would be somewhat fun to watch....)
Its really important that, early on, you assess the following big three:
1.) What do I want the car to do?
2.) What is my current skill level?
3.) What is my budget?
All three of these will likely change over the course of your vehicle ownership, but its important to look at them carefully and plan around them. The forums are a great place to help get ideas for #1, get better with #2, and completely blow #3 (although deals are sometimes out there!)
Now that you've established these, its time to start looking at the maintenance. Most people who buy a "new to me-otter" car tend to forget that its been owned by someone else for the past 20(ish) years. There are a lot of parts that wear out, and although the car will run and drive, it will run and drive much better when parts that wear are brought back up to spec.
Even before buying my miata, I started looking into the maintenance that needs to be done. Here's a decent thread on that topic:
http://mazdaroadster.net/showthread....7474#post47474
Some of the maintenance items will provide a good time to do complimentary mods. Point in case: I know I need new shocks. Sure, I could throw el-cheapo Monroe shocks at it for $60 / shock, but I want to improve upon the original design. That means:
1.) clean factory springs (mine have surface rust, and a friend had a clean set)
2.) Koni Sport shocks ($516)
3.) FCM bumpstops ($100)
4.) New dust boots ($25)
5.) New alignment bolts ($90)
That's $731 before shipping... but its all maintenance that will replace worn out parts with new parts that will make my miata more enjoyable for how I use it (autocross in a stock class.) It will handle much better than how I bought it.
For a simple project to start with, why not take apart your shifter and see if you have any bushings left? That's a good $90 VERY easy project. You've been asking about springs and bigger motors and race splitters... it sounds like you plan to race the car? Have you ever raced before? (Based on your questions, I'm guessing that you haven't ever raced in a sanctioned event... maybe a good idea to try that first? A true race car is rarely driven on the street.)
Just some food for thought.