It's not about being competitive.
I am doing it because it will improve the ride and handling of the car (ergo the safety), oh, and because I can.

I started this car with one philosophy. If Shelby was doing this car today, what would he do? I could care less about being historically correct.
Time is not much of a factor. It will take about 3 months to complete the IRS. I already have the upper and lower control arms made (uppers are powder coated already). The uprights/spindles are cut and ready to assemble (got the left one done). The bearing/hub retainers are done.
The alignment of the pumpkin was the hardest part. With that out of the way, I can get the exact axle length so I can get those axles cut and resplined.
This is the kind of stuff I love doing. It is almost as fun as driving the car.

I am applying everything I have learned over the last 45 years of mucking about with hot rods. My first hot rod was insanely difficult to live with. I was constantly tearing it down and rebuilding it to make it better. I do not need to do that anymore.
The guys you are describing bit off more than they could chew. I am not even taxing what I am capable of yet. Wait until you see the engine management system.