It really doesn't take much.
Most of what this guy did was rebuilding with different components. There wasn't much design and engineering work. This guy didn't show any special skill at all.
I say this in relation to people like the British guy who custom made turbos, inlet manifolds, adapted an Audi 6speed box and god knows what else for a Jaguar V12 and designed the entire chassis for his car too.
Or the Russian guy who MADE HIS OWN GEARBOX for his JET engined project car.
http://jalopnik.com/5302246/awesome-defined-the-10+liter-radial+engined-goggomobil
Or those Chinese brothers that made an F1 car!
http://jalopnik.com/5203610/chinese-brothers-build-working-f1-car-out-of-metal-scraps
You see, thats REAL SKILL. None of those guys look like they had anything close the budget this Evo dude had.
Any fool can buy new parts and replace old ones. And anyone who has read the manual enough times can strip the engine down too and replace connecting rods. And anyone who has taken shop class will be able to make a decent roll cage.
I've built many cars. It doesn't take much. I just know more than the average mechanic knows. But machining your own gearbox is real SKILL. And if you're doing it on a budget, more respect to you.