Holley 1850-5

Hi All,
I just inherited a Holley 1850-5 it has vacuum secondary's . Has anyone used this on a 340 4 spd ? I always liked mechanical secondaries myself. Also 600 CFM. It's a street car no strip but maybe a touch small with 20 over with Eddy heads . I am looking for some gas mileage .My AVS is giving me issues after a rebuild so I thought I might try it. I'm thinking Looking for a few opinions.
Thanks
What's your AVS doing or not doing