That's a pretty good idea I think I'll give that a go. I appreciate the help and I'll update when I've run the test 

I just completed the carb conversion on a 78 280.  Used the Arizona intake and Holley 390. Running a Holley fuel pressure regulator and the fuel pressure gauge reads  3.5.   TIming was a bit of an issue at first as it was advanced a bit with my fuel injection.  It was hard to get her to idle properly....  Retarded it some and she ran well after that.....getting good gas mileage to, but she lagged badly on hard acceleration.  Went back and slightly advanced the timing to find a middle ground and she took off like a scalded dog.......but still had a bit of lag on acceleration....so I changed plugs from the NGK BPR5ES-11 to the NGK ZFR6F-11.   That combination did the trick for me....