Read the first article on this page first:
Or you may not have a motor for long. I'm not kidding, either. Age has taken it'* toll, and you need to turn the clock back first.
Every single part available for a S2 that you need to make reliable power is available for the S1 with a little searching and creativity with the exception of an intercooler, and that'* happening right now a few topics below this one.
Rather than list all the ideas, options, and sources, please tell us your goals and realistic budget (aside from the $2k you're going to need to set aside for the trans).