Welcome to Stangnet!

You may find that to get the answers you seek, you might need to narrow your questions down a bit more, and ask them one at a time.
You say your 'stang is essentially body (frame) and interior.
These cars are a unibody design, where the subframes (frame rails) are welded to the body. What condition is the body in? is there
any rust.....i.e.: the floorpans, frame rails, cowl, trunk floor/drop-offs, rear quarters, etc., etc.....
Before you start building for any kind of power, you want to be sure you have a chassis that can handle it.....not to worry, you can get advice here on how to fix just about any of it!
What engine was in the car originally? If you don't know. look at the wheels, a 5-lug pattern is a V8, a 4-lug pattern is an I6. If it was an I6 and you want to drop in a V8, you'll have to upgrade your entire suspension and steering to V8 specs,
ESPECIALLY if you are building for power!
As for your questions regarding auto or manual, fuel injected or carbuerated, super or turbo charger, you'll find that people here have differences of opinions across the board. Read what they have to say, and decide
WHICH IS BEST FOR YOU!
btw--- I hope you've got a lot of money to spend, this can be an expensive hobby! Enjoy!
