I currently have a built 514 big block to put in a 91 coupe, but since its not in yet, I guess I can't comment on the actual streetability of it, but really, ghostdog said it best that really all that matters is the cam and tune, and your convertor/gears if your running auto. I'm running a C6 (regretfully, which I would have got a tight c4)
I didn't get the shortblock from chp or ford, just got a donor 460 block and stroked and bored with Scat crank, eagle rods, JE pistons, then blue thunder heads.
If I had to do it again, I would buy the shortblock or the longblock from one of the retailers.
Matt