When comparing duration numbers on the solid cams, about 10-15 degrees should be subtracted from the .050 numbers because you loose at least that much with lash, especially those old profiles.
It gets even more confusing with modern grind cams, comparing with 50 year old grinds becomes difficult because the lobe profiles used will affect the duration lost with lash. Some modern lobes might be closer to 8 or 10 degrees lost while old lobes can be as much as 15 or more.
The size of your BBC and the amount of compression it has will play a roll in how much vacuum it'll produce. A big player is also where they put the LSA and the ICL position of the cam when installed.
You could always request to have the LSA spread out a couple degrees to help with vacuum production (little smoother idle) Comp grinds most of their cams on a 110 LSA. Then maybe move the install position forward a degree or 2.
As an example I run a 242/248 @ .050 hydraulic roller in my 10:1 454. It's on a 110 and installed at 106 ICL. Personally I think I would have liked to install it at 104 but never got ambitious enough to dig back into it. It's not an overly large camshaft, but it's not a big vacuum producer either, idles about 5 inches in gear up here at 5,000 feet which is about 8 inches at sea level. I run an extra hidden vacuum can for the booster and that's worked "okay" for many years but it's only good for a couple stops before it needs time to replenish, which just takes a few seconds. Wouldn't want to daily drive it this way but it's been okay for a weekend fun car.
For comparison I built a 455 Pontiac for a customer, and did a custom 239/243 @ .050 hydraulic roller. 9.98:1 compression. That cam was on a 112 LSA and I installed it at 106.25 ICL. That engine made great vacuum, at our elevation it idled with 12 inches, and that number increased at sea level. It worked the power brakes perfectly.
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