Re: BBC timing advice
A few tips,..
1) Don't tune anything until the engine is at operating temp.
2) Then set the floats.
3) Yes run the VA to manifold vacuum but (against the advice above) run a can that's "all in" BELOW your idle vacuum reading. For instance, if you're pulling 14hg at idle, find a can that's "all in" by 12hg. If you pick a can that's still adding to your advance curve above your idle's vacuum reading, your idle speed (rpm) will always be in flux. Many don't understand this and find themselves 'tuining' all sorts of stuff that never fixes the problem.
4) Also (against the advice above) forget initial timing and simply time her to 34 degrees BTDC at 3000 RPM and let the initial fall where it falls. Adjust from there but you won't be more than 2-3 degrees off.
5) I never understood the notion that your PV should be half idle vacuum. Without hesitation, I'd recommend your PV rating to be 2-3 hg less than your idle reading. For instance, if you idle at 13hg use a PV with a rating of 10.5 (not 6.5 as some would advise).
6) A 750 cfm carb is a bit small for a healthy 468 so prepare for a bit of a stumble or hesitation off idle or coming out of turns. You'll cure that with bigger squirters and/or a different pump cam(s),..perhaps the "blue" cam in the two position would be a good call.
7) I think you have four-corner idle mix adjustment. Adjust them in rotation for best idle speed. You may have to go in a circle two or three times. This is important. A carb is still using (to a degree) the idle circuit up to 2000 RPM.
8) Your jetting should be very close out of the box. But confirm by checking 2-3 of the spark plugs.