The numbers you are asking for are easily doable on an engine that big. You are only talking about 1.24 HP per cubic inch. That is a walk in the park with one arm tied behind your back. The MS3Pro Ultimate or MS3Pro systems are the poor man's Haltech / Motec equivalent. It is a great system easily tunable and comes with self learning capabilities to get you up and running quickly. The MS3Pro systems support Alpha-N, Speed density and MAF based fueling models. MAF based works always, everywhere all the time — use it, you'll love it!
You are likely experiencing some form of prejudicial behavior from the guy who poo-poos your power target. The lack of Megasquirt experience with Joe from Shelby is just that, a lack of familiarity and possibly some prejudice from the early days when they offered only Heathkit style systems. Very different today. Check them out here =>
MS3Pro Ultimate and they come with a lifetime warranty — only one in the industry.
All your requests and equipment choices are realistic and very solid products. Have your friend at Shelby do your engine and ask him to use the MS3Pro Ultimate system with a MAF from these guys =>
Pro-M Racing.
When you ask why use that MAF take a few minutes and look at this YouTube video =>
Pro-M Signal Quality