Track Dog Racing C30-94 Rotrex kit, minus electronics. Has extremely detailed instructions. It is literally 100+ pages with pictures and explanations of each step. Tells you exactly what tools you need, when to use them... Anyone who can read and has one limb with a hand can install. easy 350whp 250+wtq with your built engine. Break 400whp with e85 if you have cams in your build.
Get a pnp megasquirt
get ID1000 injectors
Your transmission will brake 100% for sure. You are close to JO Motorsports (Lewisville, NC) Jason (the owner) is currently finishing my 6 speed rebuild. Cryo gears, hardened shift forks, billet shift components, coated synchros, and really, really affordable. It will buy you time on the miata 6 speed. Or prevent failure if you really keep the power/torque down. Call or text him at 336-416-2339, he will respond within an hour. Really nice guy, will work hard for you and keep you informed.
You also will need other stuff, replace as it brakes, or just go all out and get 949 racing's HD axles, tapered roller bearing hubs are coming out soon, produced by another guy on this forum, maybe invest in the O.S. Giken that 949 racing sells.
If you haven't installed a differential before, it is easy, but you must take your time with setting preload and backlash. There are informative youtube videos on how to do this.
I am very dumb. I have very little skills. If I can install good parts and do fairly major engine maintenance, you can too.
Don't be afraid. Working on cars is really easy, just takes time with the right tools. It is really gratifying. Just do it.