1973 340 Cam advice

I think the OP wants torque and if he does not increase the rear gear, then he is going to need it in the cam. Without hesitation, I would go the other way on duration - shorter- and work on a faster ramp cam, advance the cam timing a few degrees, and see if I could up the lift some. The older cams have been eclipsed by some of the later cams designs. Shorter duration with that '73 low compression engine will help torque.... more duration will tend to make it boggy.

I really would go up in the rear gearing and look at the 3.55; it is hard to go wrong with that if you don't care if the RPM's are a bit high on the open road and don't mind burning a bit more fuel. If you did that, then I would look at the cam a bit differently.

I'd look at the Lunati VooDoo series of cams and similar faster ramp cams, and put in some better valve springs. Once you go up beyond about .450-.460" of lift, you need to be looking at the retainers so that they do not hit the seals and tops of the guides. But pushing the lift up into the upper 400 range is a good step up. It will expand the upper RPM range.