I've owned my car since 2003 (?), and have been making (reversable) modifications along the way to address the concerns common to these cars.
I've kept the original engine, but it's been losing weight. Police interceptor aluminum Intake, Edelbrock heads, Aluminum radiator, electric fan, remote oil filter, oil cooler (repurposed from tranmission oil cooler), aluminum water pump, new starter, MSD ignition, Ceramic coated headers to replace the cast iron exhaust. Ceramic coated exhaust system. Re-wound alternator, upgraded to 100 Amps.
I replaced the C6 transmission with a TKO 5-speed, changed the diff gears to 3.31.
New shocks and springs. Adjustable upper control arms.
Re-routing the "fresh air" intakes out of the engine compartment, to the later position in the fenderwells.
Removing the heater, and replacing it with heat and Air Conditioning, using the original ducting.
Fabricating and installing a (removeable) front spoiler.
New stainless steel bumpers.
New gas (petrol) tanks, now in welded aluminum (as opposed to the braised and soldered steel originals). We took the old ones apart and reproduced them as per original.
Upgraded lighting, including Lucas "square 8" driving lights.
I've identified the rubber bits, and am replacing everything. Window felts, channel guides, vent window seals, fuel neck grommets, etc.
I've saved practically everything that came off the car, except the original radiator, which I foolishly threw out in a fit of cleaning up my garage.
There is still much to do, but the car is SO much better now. It does not overheat, the oil temp is under control, it's quicker and handles better. No squeeks or rattles, it feels taut and "youthful" now.
I am so lucky to be living in Southern California where the original Shelby guys are still at it. George Petreus, Mike McCluskey (who builds airplanes and cars for C. Shelby), Dennis Cann and others who know these cars well. It's as good or better than having the AC factory still in existance.
Paul (Classicus) - are you still there? Haven't heard from you for a while. I hope you're well.