73 340 SB Rebuild, Need Help Selecting Parts

You are on the right track with wide torque band: I rallied (SCCA, NASARallySport, RallyAmerica) for a long time and it is the same thing: wide torque band. The low cranking pressure makes sense with those pistons; those look like low compression after market pistons. (With that depth in the hole make sure it is not a 318 !....340 standard bore should be 4.040".)

To get that wide torque band and that power range, you are going to have to push the compression ratio up to around 10:1, get the breathing up, and then use the right cam without too much duration. You should be going to different heads with more breathing to make it to those HP numbers. Or porting yours and opening up the valve sizes. Look at this link for a while to see where your head flows need to be; the EQ or indy-X iron heads, or Edelbrock aluminum head flow numbers in their stock form are where you need to be shooting for.
#1---Head Flow Charts & Comparisons

Both of those above heads have smaller, so-called closed combustion chambers so will make it easy to get the CR up. That is what you will be fighting with those stock heads: the open chambers take a different tactic (lots of shaving and standard early 340 pistons that stick above the deck) to get the CR up and you still cannot get effective quench out of the setup. Quench is an aid to avoid detonation, which will be important here, and also helps combustion efficiency.

For CR in the right range with these closed chamber heads, you need to go with some flat tops and put them near to zero deck. KB243's are one choice; they are hypereutectics and light and I have rallied on hypers with 14-15 psi boost with no issues. There are also Ross pistons for forged units, which would be good for durability in this use, but forged are heavier. Lighter pistons and rods lowers crank stress.

To fight detonation with a shorter duration cam used to keep the low end of the torque band alive, aluminum heads have a distinct advantage. I personally would go straight to the Edelbrocks and minimize the detonation issues and get right to the breathing numbers needed.

I'd be reconditioning the rods, or, better yet, going to SCAT rods, which are lighter.

Look at the oiling mods in the stickies section of this subforum. The high RPM stuff is less applicable IMHO; I think you will need to consider a slightly deeper pan built with baffles to keep the oil around the pickup. And I'd put in an oil cooler and remote filter to add oil capacity and cooling. Those don't cost a lot but add a lot.

The intake and headers are good; just stick with what you have.

One more word; if you sre $$ limited, consider selling the 340 parts and get a 360. There are more pistons choices. The rest is the same cost. I say this because in my view, the ideal engine really only uses your block and crank. If you like the 340, stick with it; those 3 numbers in that sequence truly do have a certain mystique, but the HP does not care what produces it.