Are 340’s rare

Why so small. :D
That's what she said.
All kidding aside.
When I got a virgin Mopar X Block (race block)
I had options of what to do with it.
1st off the casting says 318 and takes 318 mounts. Since I have only ever run 340 blocks and tossed all 318 I ran across had to find a 318 mount.
I had a early 340 someone gave me cracked block. And had steel crank 10/10, reconditioned rods and TRW standard forged early pistons/rings and balancer.
Machine shop had a cracked TA motor so could gave gotten the Heads, and valve train. They also had a de-stroked crank. So thought about making a 302 with a solid cam a size of 1968 manual 340 or 1 size up larger.
I saved the cash and used what I had stock 340HP high compression.
So stock stroke 340, stock 4.040 bore. Spent money on closed chambers album heads, and roller rockers.
I bet the 302 six pack would have had good street fun.
Other options possible since virgin race block could have also been stock 273 bore or 318 bore and left more meat for later.
But think only option back then would have been call and get costly custom 273 or 318 pistons
so could have also been a 273six or 318six. Who would have known.