would a cobra upper and lower intake and a set of gt40p heads bolt right up to a 90 mustang gt without having to change or block off anything other than the headers?
Not sure what u mean by "block off the headers" but...
The cobra intake and gt-40p heads will bolt up just fine.
Just remember that the gt-40p heads have a different spark plug angle than the stock e7's and pretty much require a different header than stock to clear the plugs. Some people get away with using a modified socket and using heat shields on the plugs but it seams to be hit or miss with that method. Also, the cobra intake has a built in EGR provision so you wont need ur stock egr spacer deal.