It took be a while but knew I had read Kenne Bell specifically recommended the Holley 850 for the 350: "INTAKE At last - an aluminum intake manifold for the 350. Kenne-Bell calibrated 800 cfm Carter is the best carburetor for stock or Stage 1 TA manifold. Stock carb is 750 cfm, so don't waste money on a 600, 625, 650, 660, 725 or 750 carb. The little 350 likes the larger 800 Carter [ also good would be an 800cfm QJ from a 455, bob k ]. The 850 Holley also works but the TA manifold is designed for a spread bore type carburetor in the 730-850 cfm range. The Kenne-Bell KB46002 Air Cleaner is designed to fit the Carter 9800 carburetor while clearing the stock Skylark/GS hood. The KB46002 is so efficient it will not decrease performance or horsepower. In other words, the 350 will run as well with the Kenne-Bell Air Cleaner as it does with no air cleaner at all." He does not mention if he was running vacuum or mechanical secondaries. Here I need some schooling. I thought it was simple until I started reading the interweb. So what is the difference between the two, advantages, and disadvantages?