I'm considering purchasing a new Holley 670 Street Avenger carb. I see Summit has this carb. in part number 80670 and 83670. Doing a side-by-side comparison it looks as though they are they same with the exception that the 83670 is aluminum. However, the aluminum version is $26 cheaper. I would have that the aluminum would have cost more. Does anyone have any experience with these carbs. and if so, is an aluminum carb. a pro or con?