.....I identified my Holley 750 double pumper by the numbers on it. The motor is back in Kansas now so I can't go look to see exactly where the numbers were located but they were on the outside where I could see them. It had the model number on it {in my case xxx4779}. I then went to the Summit web site, put in '4779' in the search & my carb came up .... I thought I had an 850 but no it's a 750...... hope this helps ya, Bill
ps, if you still have problems I'd call Holley.....