A couple of comments
I'd likely go with an iron block, especially since you are painting it. In the end FAR easier to maintain clearances and have an engine with very consistent and long lasting performance. Lots of passion either way, but in the end, aluminum moves and grows more than iron, it's fact not opinion. You need to build around it, which you can, but way cheaper and much easier with iron
You can do what you want with a custom cam, in fact, I'd likely go hydraulic roller. Wide centers to reduce overlap and lift to support the heads will allow it to pull real hard but still have vacuum. With a set of good heads and the dual quad, shooting for about a 6000 rpm peak and a 6400 shift point you should have a very strong combo.
As far as the rear suspension, don't worry about what they did in the old days, today are the good old days LOL Caltrac mono-leaf and traction bars, gusset the spring pads, and these cars drive off the line gently and just scoot compared to the old twisted wheels up of the old days.
For cooling, you'd be amazed a how "un-fussy" these engines are. My Mustang 489 powered, with A/C to boot, has been from VA Beach, to Vegas to DC to Nebraska, and it uses a simple clutch fan, shroud, and aluminum 2 core cross flow radiator. The key is ensuring the water pump and fan are at or slightly above crank speed, and that the air has somewhere to escape. In my case, mine is sort of a Boss 9 clone, so I did not seal the hood scoop and it made all the difference sitting in traffic. However, the other big contributors are a fan that moves plenty of air (far more than any electric that would fit) and ceramic coating the headers while running fuel lines away from heat.
I did add two small electric fans to the a/c condensor but that was because the switch to R134 wanted a little more air to keep pressures right, those actually do not contribute to the cooling.
Sounds like a mean Mustang!