honestly your bouncing in so many directions what you will end up with is a pile of parts and a car that doesnt run. you need direction. if you want a 300 hp n/a or s/c 3.2 or n/a v8 or s/c v8 decide and stay on track.
dont buy anything until the build list is complete with what you want to accomplish. if time isnt a factor then dont let indecision be a factor either. personally if you can get the n/a v8 parts for nil thats the route i would go. it will be fast enought to put you in an early grave and still put your ride in an elite class.
remember the engine is only 1 part of a fast agile SAFE car. suspension, braking, trans, driveline and rear diff all have to be considered as future upgrades to allow the engine to perform at its peak