That combo will give you a starter gear of 9.21; a little tall for a 340, but you're a couple of hundred pounds lighter than my S-clone, so , depending on the rest of your combo,it should be OK. At 3100 your tires would have to have a roll-out of 76.24, or about 24.26 tall. That's a pretty small tire; Like maybe a 215/60-14 . You probably wouldn't want to run something that small on a 340car.
More likely you'd run a 245/60-15 @26.7" tall, and rolling out at 83.9 inches. This would get you 2817@ 60 and Zero-slip, ie with a manual trans.
But really, with a 340 you should be running the tallest widest tire that will fit, on a wheel well-centered in the tub, whatever it takes.
And I'll tell you why; cuz if you don't,and if you run a DP carb; there's a VERY good chance, that she'll be sideways at the oddest times, and pointing backwards some of those times.Don't ask me how I know, I'm 65 years old and learned to drive in a 70 Swinger
That taller tire will throw your speed-O out about 10%.... and it will make starting out require a bit more rpm than before.
I run a 27 inch tire,with an HO 360, and wouldn't want anything less than a 10/1 starter gear. We'll see how your 9.21 works out. If you got a 292/108 cam Then you're gonna want a whole nuther comb,lol