i would say your in the ball park if it picked up that much ( you knew this one already lol
).
i assume your valves are 2.02 or 2.05...any major head work ?..any port work to intake...and last what size cam are you running?. is any work been done to the 650 including milling down of the horn?
what are the jet sizes in the 650cfm compared to the 750cfm
I have run simliar size motors on the street/strip many times in the past .
the 650 cfm really was responsive on bottom end..
i have a 406 ci 460hp steel head ( iron eagle) heads, no port work, 520 lift flat tappet cam...i have out of the box 750cfm ( with horn) and it takes all of it....
30 more cubic inches is all i see off the top..
have you checked you plugs after a run ?...be sure to kill it after a full throttle attempt...you can also get a pyrometer to get some exhaust temp readings ..this will tell you lean or fat for sure..
sounds like your right on top of it to me.
Brian