I’m looking to replace the current Holly carbs I have, but I can't figure out what they are...   I have been trying all the #'s I found on them just to get nowhere.  If you can help me to know what I have, I would appreciate it.

All the #' On the Holly carbs (Center top) 4150 hp, (R. side middle) "list" 805761 under this # is 1566,(R.side bottom 11874BR under that HP, (on left side) 11938
 
Thinking about getting two, Mighty Marine Demon 825 CFM Supercharger Carburetors to replace these warn out Hollys.  I know less than zip about carbs and want to get the correct ones. 
I have a Chevy 502, 6-71 or 8-71 Wieland blower not sure which (how to tell) Not sure about the cam either... Sorry all I’m just trying to learn, if you need more info I can try to offer it