You will probably get a better answer if you ask on the Shelby forum:
www.teamshelby.com
There are options, one from CoolTech (one of our Ford GT accessory suppliers). It is described as a Boss302 kit but might work but would also require a rear-seat delete kit. Ultimately it will depend on the inspector if he lets it go by. Maybe someone here has tried it but like I said I think the guys over at Team Shelby will probably have more experience.
I dragged my Shelby GT/SC at Bandimere, and with a 13.6 I had to have a helmet and fire jacket (not suit). I was told below 13.0 and I'd need a fully functional 4 point roll bar, but don't know picky they get about permanently installed vs. bolt in.