Not sure about 70, but in 71 many hi performance parts could be ordered on the GC. My 71 Gran Coupe has the Hi Perf 383 4 bbl, the HD 727, the 8 3/4 posi rear, the rally gauges, special Rally susoension, swaay bars, power steering, power brakes.....the list goes on and on. I have heard two opinions on my car (1 of 79). One is that perhaps an older man wanted the luxuries and also the hi performance Cuda stuff, so he ordered the best of both worlds. The second opinion is that with the way insurance companies were treating the muscle cars with the high premiums, someone ordered a Cuda in sheep's clothing. It has many of the items found on the Cuda, but would have been under the insurance companies radar.