well i had the single pattern 256* .425 cut on a 108 lsa in a 318 powered valiant it 18 mpg combined city/highway with about 15" of vac.the 256/262 cam was in a 3/4 ton chevy truck with a 350.it had stock vac and a very slight chop to the idle.if a stock/smooth idle and vac are a concern to you you could go with a single pattern 256* 425 lift 112lsa "supercam".
