Richard,
I live in the Peoria, IL neighborhood, and had an Intermeccanica built in 2005. My car is an air-cooled speedster with a gas heater. It was never meant to be a daily driver, but I'd been through two pan-based speedsters with other builders- so I really knew what I wanted. I LOVE my car, but even with all the experience I brought to the build, there are several things I'd do differently if the chance ever came up again.
What I would recommend for a daily driver is this- unless you absolutely MUST have a speedster- I'd get a Roadster (Convertible D). It's just a far more practical vehicle with the larger side windows, better sealing glass, higher top, etc. I had no intent to drive the car daily- but even so, I thought long and hard about it. It's the biggest single choice you'll make.
Doing a Roadster opens up the whole world to more practical things. The seats that Dale recommends ride a bit higher in the car than the speedster seats, and as a result are much better suited to the "D". They are better seats, and would be the first choice for daily use. I'd get them heated (in leather), without a doubt. I'd also skip the square-weave, and get a stereo that was hidden from view.
The powerplant is the key to the next set of choices, and what do do depends how "retro" you want to be with the car. There is no doubt that a watercooled car is functionally superior in every way. It will meet emissions, will start and idle smoothly when cold, and will have manners like every "real" car produced since about 1990 or so. A water-pumper has a radiator, and a heater core. Heat is vastly more important to using the car every day than A/C in this part of the world. Adapting A/C to a water-cooled car also has no ill effects.
If you want the real-deal-air-cooled mill, plan on knowing something about how to work on it, because nobody in the Midwest remembers. If you do an ACVW, you'll need real heat, and the only way to get it is from a gasoline heater, and they are far from perfect. IMHO, A/C is a bad idea with an air-cooled car, but you'll miss it less than you think you will. That being said- the whole air-cooled thing is really "it" for me, and part of the essence of a 356. I'm not a mechanic, but I play one on TV and love working on/tinkering/improving my car- if this isn't something you like, or have any experience with, I'd never go this route. Proceed with caution here.
I'd get Henry's stock suspension set-up in a daily driver- and wouldn't do the stiff torsion bars, sway bars, or Konis. They are great for the whole cafe racer thing, but for a daily driver, just make the ride rougher. I would do a rack and pinion and four wheel discs for sure.
The rest is just personal choices. It's enormous fun. Good luck with your build, you'll absolutely love working with Henry.