Carb CFM.. Increase?

I think I know the answer to this but I figured it couldn't hurt to ask.

I bought a Proform 650 Race Mechanical secondary carb for a pretty healthy 318 last year. I really loved the carb. The car started right up and ran great with it and was very responsive and I ran an A/F guage and it seemed pretty dialed in OOTB.

I am building a very healthy 408 now. It will have 254@050 mechanical and Trickflow heads. I am wondering if anything can be done at a reasonable cost to get that one to flow a lot better? I think 850 is ideal for my build.

I see a new proform 850 mechanical race is 600 and i'm sure thats what I will end up doing and I hope sell this one and get some money recouped.