I like my Holley 600cfm double pumper, but it is expensive as it uses more fuel than a vacuum secondary carb would. I have a 302 4bbl setup, manual trans.
Ive got a Barry Grant Speed Demon 650cfm Vac. Sec. for sale. bought it off here, awesome carb, but i m going to swap to Fuel injection so im getting rid of it. PM if you are intrested.