If you want to pulley down(if you don't go turbo) and minimize the chance of Blowing your motor up then you pretty much need headers.
Headers would be worth it if you nut up and install them yourself but you don't want to but you think a turbo build is going to be easier....you'll be in for a shocker.
anyone that tells you that you need headers to run smaller supercharger pulleys has never even attempted to without headers and is just regurgitating information they read once upon a time.
But the crossover and rear manifold don't pose any real restriction, right?
So, just need something for the front. I don't see anything really being THAT much better than an SSPLOG + 3" Downpipe.
By the time you buy a PLOG and DP you could just get SD headers for $200 and call it done.