I just read the heat, a/c and stereo part.
Cobras are small. Little British Car small. They're an AC Ace after all. I have size 13 feet and I have to drive it in my socks.
They're incredibly light too. I almost shoved ours off the jack stands pushing the lower control arms in to the brackets. I would bet that the fiberglass cars are heavier than the originals.
They're 10lbs of crap in a 5 lb sack. The originals have a heater but it's really more of a heater shaped object. Hot water goes through it and it has a fan, that's about it. You wouldn't be able to cram an AC suitcase under the dash, there's barely room for the instruments.
The car doesn't really need a heater since there's about 3/16" of fiberglass between your feet and the exhaust.
Stereo, not likely. Doors are thin and there are no inner door panels, just some leather. There are no kick panels, no room behind the seats.
You don't need a stereo anyway, you've got a V8 and a manual gearbox.
I don't know what all the replicas are like but if they have things like inner door panels, speakers, A/C, etc, it might look a little silly. An AC Cobra is just enough removed from an all-out race car to be street legal.