71 340 Compression Test

If you are gonna spend money on it and are thinking making power, a quick swap to a 3.58 stroke, (or more of course), is cheap way to more off-the-line torque. The extra stroke will allow you to run a bit more cam too, before loosing Dcr, and a bit less TC. Between the two, you might be happy without any extra head-porting.
An acquaintance of mine did that to his 340, and shaved the piston-crowns to fit X-heads with "pretty good quench",(his words). That motor was plenty strong......
I highly recommend to select/buy a cam after your Scr has been measured.
And streeters need the fastest cam lobes you can find, and are best selected at under 230*. Even 230s in short-stroke engines usually need gears and a bit of a TC
You can't really have a cruiser and a "shut-em-up" sbm-car at the same time, if staying NA (normally aspirated). If you insist on it, you will likely be disappointed.
To shut down a 383 in a similarly weighted car, you are starting from a 44 cid handicap. You are down 11.5% on cubes. To make it up, you are gonna have to build nearly a race-engine. If he is at 1.2 hp per cid, then he has 460 hp, and you are gonna have to make 1.35 hp/cid. Which, while doable, is not cruise friendly. You are gonna have to make a decision, and it might not be cheap.Having a 460hp/340 is just the beginning.
After that comes; the rest of the powertrain,engine support-works,the suspension, steering and brakes, frame connectors,traction aids, sticky tires, and safety equipment. Up here this could be $16000CanPlus. Maybe closer to 20/25 if you have to pay labors.And that doesn't cover maintenance, breakages, and rebuilds as weak areas come to light.That's a lotta coin for bragging rights. :(
You may remember 340 cars as being fast, but you have to also remember the times.