I have a stock 360 in a 68 2wd with a c6. It has a 2bbl intake and I am going to build a 4bbl 390 when $$$ permits. My Holley 2300 is needing a rebuild, and I could trade for a 500 cfm Holley 2bbl that needs rebuilding as well. I then wondered if it would be better to just go ahead and find the 4bbl that I will use on the 390 and use one of the adapter plates until I am ready to put it on the new engine.