Preparing to do a auto to manual swap

If you can find a similar donor car then most of your battle is won.

Brewers is an excellent source for parts and info just don't wear the poor guy out too much without knowing a little bit about the process and parts from doing research.

You're gonna have have to cut your floor and weld in a four speed hump and my advice is
To yes go ahead and cut your trans tunnel so your four speed linkage will clear and then install your trans with shifter and linkage BEFORE you weld in your new 4 spd hump.
There is usually some additional grinding , hammering and tweaking that may need to be done to get your shifter to fit nicely and allow access to the bolts securing the shifter mechanism.
I built a custom console around my shifter to finish it all off nicely.