carbs are tricky
Bone
Tricky question
I think that carb will work QF's are pretty flexible for tuning.
I have had about a dozen BBC street strip motors, from 396 to 540's I have ran 750 vac carbs, 750 DP's, 850 DP's 1050's 2 and 3 ckt etc.
Many folks on here have more experience than me,but I think you can "detune" or set that one up.
As far as the carb calculators I have no faith in the ones I have used, they always came in at way under the CFM I thought I would need.
your motor seems to be lower compression but still may move alot of air. based on the previous owner reputation.
I would "play" with the carb you have.
Again just my opinion, but as you know we have some slick guys on here they may know better than me.
Good Luck
Jeff M.
PS I have asked about carbs issues on this forum and got great advise