I got SPF 1676 also with a single roll bar.. I had the dealer install the shoulder harness(s) before I took delivery. I added the anti-sub belts by ordering from Simpson- I ordered the six-point version and used the front seat mounting bolts to secure them to the floor.
http://www.simpsonraceproducts.com/p...21&prod_id=896
The insall was real easy and the belts for both seats cost aprox $50. (including shipping).