Are the claims on the 40SS w/twin 6.2's 63mph real?
I'm leaning to that boat if it is or will consider the 29SS sea Ray w/350's 320hp

Not a chance
My 06 400SS with 525's does 60.
If i had the canvas off and low on fuel would be more but probably not a lot.
Kind of a night and day difference between those two boats.

Comparing a 40 ft Formula and a 29 ft searay?? (btw, I don't think you can even get the 400SS with 6.2's)

Can't be. My 292 is listed as 7000 lbs and with 6.2's runs 70 mph. The 40SS is 16,000 lbs. Must be a misprint. The 40SS is available with 8.2's.

yes, its a mis print. I meant the 280SS

The 280SS is a big and heavy non-stepped deep V. I don't have any first hand knowledge, but 63 mph seems a bit optimistic. I would think mid-50's is more like it. If you know the year, power and outdrives, I'm sure Formula can answer your question.

Expect 52-55 out of that package.