Hi Chris,
If your rad does the job for you, then it's the right one. Mine didn't, when mounted in almost the same space. As I stated above, it got CLOSE to proper cooling with the deck lid removed, but blocked too much exhaust air with it mounted. If you have a single or dual fans, a shroud or fan housing is a must. My new configuration for the deck lid will be almost all open space with an open mesh grill.
Be aware that almost all fan manufacturers, including Spal, make different CFM fans for the same diameter, i.e., Spal will have a 12" pull or push fan with thin line motor that puts out 400 cfm, 12" medium sized motor that puts out 700 cfm, and a really large motor that puts out 1400 cfm. I am making up those outputs, but you get the idea. The thicker the motor, the greater the distance it protrudes from the rad. If you have the room on top of the rad, which I may with my new deck lid configuration, my suggestion is to install the highest cfm, largest motor that will fit. The large fan motor will protrude almost 4" from the fan shroud. Spal makes a LL motor, or long life, and also makes a VLL type of motor, very long life, that will be useful since mine will be exposed to weather. So, in addition to varying amounts of power for the same fan, you can get a better-sealed motor that will withstand weather better.
By the way, I had my car at Outfront for a while about a year ago. They were able to address some, but not all, of my cooling issues. Like many of the big names in the car game, your guy, Steve Johnson, has his fans and his detractors. As you may have discovered, it's hard to find a shop that will even look at one of our replicas, never mind do quality work in a timely manner.
As owners and/or wrenchers, we're allowed to make lots of mistakes, and spend lots of money, we're just not allowed to quit. If it was easy, everyone would be doing it, eh?
My apolgies, feufeu. This now seems to complete a total hijack.