big 'ol lol there… A cheap custom 6 point usually starts around $1500 and goes to $3000 for a super fine fit, I would only guess that a basic 4 point would be $500-$750 range.
I really wish I could recommend some to do the work, I really do… :roll:
But why do want only the rear stiff? Even if you don’t want to deal with a full cage I’d still attach a diagonal door bar to the driver/passneger footwell area.