The 268 would be lazy if the stock converter is retained and the rear gear was numerically low.
The cam you posted specs to looks like a actual OE 340 cam. Is this correct?

Scott, I hate to badger, but we need some more info/help on this build.
What is the rear gear & tire size?
Is a converter change an option? Unless it is a manual trans?
Is the engine going into a full rebuild?

Other than the above recomendation I made about the Comp Cam for exhaust manifolds, I normaly run a split duration cam with unported heads with headers or not, with 8*'s more exhaust. Thus helping with the corked breathing.

Iron headed engines with small cams work very well with a 9.0-1 ratio. (In case this is a full on rebuild.)

...stock 340 lift with much less duration,ideal for a heavy vehicle ..nearly every manufacturer sells a similar grind

Had a HP 360 in a 74 RR with a 4-speed. Same basic cam as a 340. Was plenty fast. With the 73 Charger I'd put 1.6:1 rockers on the list. Shave the heads to get as much compression as possible. Pocket port, gasket match. Put a strip kit in that TQ. IF budget allows put more converter & lower gears.

Scott,contact AJ at BGR,he has a 340 engine complete that has 6 pak heads and flat tappet cam,polished single four Mopar intake,polished aluminium valve covers,Roller rockers,deep pan,Fluid Damper and extras.It was in a 3400 lb Cuda,rotating assembly is balanced.We built this engine back in mid 90s and it just has been setting around.It ran consistant low 11s and in good air ran 10.90s.
AJ at BGR 412-216-4727