what are my options to hook up racing harnesses?

[bobafett]

my seats are garbage in my 240, and i have a friend who can get me a reaaaaly good price on some racing seats... now i have ridden in cars with harnesses, and really liked the feeling while driving really hard...

my question is, what do i need to install to my car to safely install harnesses? at this point im thinking a 4pt harness is all i need.

from my research it looks like a roll bar is the answer, what options other than autopower do i have for an 89 s13 hatch? also where would i purchase that roll car?

is it safe to use harnesses with a c pillar bar?

if i were to get something welded in custom ,and not off the shelf, what do i need to implement to get the harnesses installed properly, are there certain mounting points that are critical? the only factor i am aware of, is that you should have the upper points of the harness even with your shoulders, and not mounted low like on the floor, so that if you crash the belts will not compress your spine.

anyway whats your input on the easiest, cheapest or best way to install harnesses with some racing seats?