Can't say enough about
http://www.nationalcarburetors.com/
Ordered a carb for my specs, when it arrived all I did was bolt it on, nail it and smile.
For the price they charge, even with the core charge you could resell their carbs for a tidy profit.
You can't beat a well tuned qjet unless you need a carb bigger then 800CMF
Though its best to always have the Doug Roe Qjet performance book, he deisnged the carb for GM.
I also perfer the straight shot inlet of the BOP carbs over the side inlet of the Chevy ones, reguardless of what its for. Putting one on a Ford, straight shot one plz. They also come with the easy adjust base, no special tools needed.
But I have had to do nothing. Though I did install a manual choke on it instead.