Well, if I’m not wrong, most of the guys at SPA didn’t particularly prepared for AIEEE architecture course or NATA. They studied for IIT but between they gave exams for AIEEE engineering and architecture course.
I don’t know if there is a particular preparation center for getting through to AIEEE engineering colleges. My recommendation is that if you are good at logical ability and maths with simple drawing skills then you can make it to good architectural colleges.
A comprehensive answer can only be give by SPA students in this case, which you can find in this forum.