Need a plan - component selection for restoring 68 340 that runs on 91 oct

Hank'sFs
were you thinking of this comp cam
20-309-4 - Magnum Muscle These cams follow the tradition of COMP Cams® excellence and offer a step up from original equipment cam designs.
or this one
20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts
both these cams are shorter on the seat than the 340 cam and should work with slightly less compression
However they still leave a lot of torque on the table- especially the XE-268H which is a 1977 Harold Berkshire profile for chevys - pretty big spread on the exhaust
here is a 268 Voodoo
494/513 268/276 226/234 108LCA 110/106 1800-5600 Voodoo remember .006 268/276 is not the same as MOPAR 268/276
474/494 265/271 220/226 110LCA 112/108 1400-5800 Lunati Voodoo

here is a quote from well respected JRobb (264 HR but that's not really relevant here where we are trying to determine duration and compression- some realistic numbers
.485/.485 264/270 213/219 112/106 Lunati SBM HR 1200-5500 headers 3:55 RAMM's cam

“371-374 hp @ 5100-5200 rpm to 5500 rpm where it was down about 1-2 hp from peak.

428 ft/lbs @ 3900 rpm. 423.8 ft/lbs @3250 376 ft/lbs @2500

. Idle vacuum was a steady and smooth 15-16" @ 750-800 rpm.

Total timing was wound up at 37-38 total likely due to the low compression and no real quench to speak of. A half inch spacer hurt power everywhere.

I feel that a 750 dbl or even a 650 dbl would likely crest the 380 hp mark and then some.

Manifold vacuum was registering 1.1-1.3" in the upper third of the pull indicating the carb is on the small side and presenting a restriction.
These heads are ported. This engine is about as tame as it gets.

It almost matches the output of a Mopar 380 hp 360 crate but with FAR better manners/driveability and on cheap fuel and likely a bunch cheaper to acquire as well. J.Rob

here's one size smaller If you have no quench and the lower compression you go the shorter your cam needs to be to keep low end
.475 262 220 VD
want more at 262 @.006 duration
494/506 261/267 214/220 110/106 .904 Howard grind not hard to get more dynamic compression and more lift (breathing)
cheers