650 / 750 Double pumper Holley

I currently have a 670 Street Avenger on my car (340 challenger, 727 tranny 410 gears) and am looking to change it out to a double pumper. I can buy a new carb but that will cost a fortune, I've never rebuilt one and am looking for a good core to start with. I just installed my first transmission and it's got me wanting to do more by myself. I've got a friend who will help me with the rebuild. I want something that I made not store bought. 650 or 750 cfm.
Anyone got anything thats not being used that can help teach and old dog new tricks?

I've got a Strange Spool for a 8 3/4 489 case I'd be willing to deal with. 32 spline I think.