I did the 500" stroker kit using a 400 block. It does fit better (inner fenderwell clearance) in an A-body for exhaust and A/C blower motors (sometimes the master cylinder, too). Exhaust is where you're going to chuck out some heavy dollars - you don't have many choices and they are all relatively within the same price range. This is assuming you don't buy a cheap set of $300 headers from Summit and beat them into place (although, you technically could).
The TTI/Tri-Y setup has been my favorites for the A-body builds. They drop right into place with the motor locked down and you don't have to remove the steering column to get them in (I didn't).
