Hard to say if they would flow all of 800, but the combination of large valves, small chambers, big cam and the 472 intake could handle quite a bit. One problem that I know mine had (until I swapped it out for a 850 DP) was a noticeable hesitation, almost a bog, due to the small accelerator pump shot off idle. Fix turned out to be swapping the squirters, or drilling them: ultimate would be to use a Reo 50cc pump and cam, which would give enough fuel to get through the flat spot.
I ran the 850 for years - never a problem with loading up, or bog - of course, the 12.5:1 Manley's and the Sig Erson stick I installed in '75 may have stilted the results somewhat. The 302 would rev to near 8000 in stock form; I did this numerous times, until I snapped a stock spring on cylinder 4 (changed it in the parking lot of my dorm). Still have the spring, and no, it didn't drop the valve. Dang lucky -