Comp Cams Xtreme Energy 268 ?s

Since we haven’t heard from OP, let’s back up and see if we can connect the dots…
OP said this cam/lifters came out of a ‘65 273 that wouldn’t support it, not what it’s going in, and if it’s going in the ‘71 dart with 120k in his avatar I’d be surprised if its a 273. More likely it’s a 318-360 that may or may not have power brakes to support. I’ve got the same cam in my mostly stock 340 without power brakes but even so, it’s pulling enough vacuum to cover them. Long/Short is we need more input.