This really is a tough line to draw.
I've spent too much time not reaching any conclusions also.
At this point, I'm drawing the line at welded-in, high door bars, and a containment seat.
Going to try to "settle for" welded in bars at seat bolster and another angled at shoulder height, and a Sparco street fighter seat, w/ 6 point belts.
Maybe include a higher door bar, with pins.