There are quite a few options as pointed out: cockpit adjustable roll bars as well, traction control, fire bombs, 4 and 6 point cages, race replica paint schemes, 6 speeds, LSDs, BRM/Halibrand, periscopes, gurney bubble, race harnesses, various leather trim, gauges packages (mech/elec), full heim joint suspension (old style was mostly so), powdercoating colors on frame, panel material, left/right drive, center/right shift, MKII option, MoTec/carb, and a new others. Many of these can be done to any GT40 at any time.
One thing I do like is while RF will do a lot of different race-slanted performance options they do not stray too far from what a lot of folks here consider "GT40". Gauges, wheels, look and feel seems to revolve around a standard GT40 style look without the flashy factor.