That 850 should work just fine. Those XP carbs are very nice to work with. For max power you could go larger but it might not drive as nice. For street driving I'd use a really nice 750 carb but it will give up a little bit of top end power. If you are computer savvy you should consider a Holley Sniper EFI setup since it will do a lot more for you for not much more money. But if you aren't computer savvy then don't bother since it is easy to get lost in an EFI conversion.