Re: cam and top end
that's a big HP difference between 400 and 550....heh. I'd go solid roller cam if you really want to make some power. You can go to the 215cc heads if you plan on spinning this motor up as well. Is this track only, some street? etc etc. I don't have a problem driving a 3600 stall and a 4.11 gear, which is mild compared to some buddies who have 5500 stalls and 4.56 gears in their cars. It's all up to how radical you want it to be. The new dart platinum heads are a good choice and flow better than the older ones as well.
How fast is it? That depends on who's around