Ax-15 to A833 swap

Well if 80 mph is your cut-off point, and with 4.30s, you have a three-gear car, for 80=6000.
And since racing is Not on the agenda, but the small-valve J-heads are gonna get some attention, you can build for peak-power at or near 5300 to say 5500, at most, 5700. That's gonna be about a 230degree cam. With a proper tune, that's not gonna rumble much. That is what I have in my 367. To hear it, I gotta retard the Idle-Timing and idle it down. With a shorter stroke 340, maybe you'll hear it.

Here's the thing; if yur shutting down at 80, then yur not bucking much wind, and so, you don't need Quarter-mile reserve-power. Which means that you can run a smaller cam, and less gear. Which means a reduced Cruise rpm.
AND
with 4.30s; 30mph is ; 4300 in First/3100 in Second/2250 in third ...... so, if you are plunking along at 2250, and you get the urge to floor it, The 3-1 shift is very awkward, and when you get into it, yur only gunna be in it for a second, and then into Second gear you will go.
But if yur burbling along at 3100 in Second, with dual 3" exhaust pipes, yur gonna be pissing almost everybody off.
BUIUUUUT if you go to Second, this is only 3100, and the 340 is NOT known for making torque down there. So, yur gonna have to wait until about 4000 with that 230* cam, which is 39mph. Course, if the tires light up, that's a different story.
AND
since you are already moving, Torque-multiplication off the line is not that important. Therefore, IMO, for maximum smiles, you want a gear at 30>35 mph that is at or just below the torque peak. Suppose you picked a smaller cam that torque-peaked at 3800. and you geared that to 30 mph. Now yur riding a rocket. This would be a roadgear of 10.17. Your choices for rear gears are 3.82 for first gear, or 5.30s for Second. So obviously, for a streeter, yur NOT gunna pick 5.30s.. So now, since there are no 3.82s for Mopars, your sub choices are 3.91 or 3.73. For a 340, I would probably go with 3.91s; for 30 =3900 .. Now when you stomp it on the 2-1 downshift, at 30 mph, you are definitely smiling. and first gear could go to 44mph@5800, then into Third at 4200, so again, the car is poised for performance, and 3.91s will get you 80=5450, just after peak power.
The only down sides to 3.91s are
1) a starter gear of "only" 10.40, which means that to get moving, will require a wee bit of forethought, with either more rpm to get moving , or don't try so hard to be a Mustang.
2) 65mph = 3170 rpm., still better than 3470 with 4.30s

So, in this scenario, yur looking for a cam around 224@050. and put the power in the heads. so you don't need as much rpm. Which, if you don't put bigger valves in the 360 heads, is gunna be a bit of a stretch. Well unless your Js are off a 340, lol.

As a streeter, over 90% or more of the time, your engine is gonna be at under 4000rpm. Those short bursts to 5500 or so, hardly make a ripple in the average rpm that she will be seeing. Therefore, to my way of thinking, having the combo geared right is way more important than whatever absolute power she makes. Most of the life of a streeter is spent below 50mph, so Ima thinking, getting to 50 in a blaze of glory trumps getting from 50 to 80. I mean, that's my thinking. and since I have tried about every gearbox and rear gear available to Mopars, over 55 years, I have never been happier than when I put Second gear where it needs to be, and forget about everything else. It doesn't even have to be perfect, as long as it's close. Now, I haven't had a running 340 since 1984, so I've been a 360 kindof guy ever since. This gives my combo 20 cubes of low-end grunt , and allows me to drop another cam size, which then gives the 360, an extra portion of cylinder pressure thru-out it's rev range, which is a real pleasure to drive.
When I initially installed a 230 cam, where a 223 had been, I rightaway noticed the loss of bottom end torque, and I spent several weeks bitching and moaning about it. The only cure was a lower first gear, so I got me a Commando box with a 3.09 low, for 16% more torque multiplication, in first gear. That allowed me to reclock my cam back in to straight up, which stretched my top end back out . The following winter, I pumped the Compression ratio up a little during a routine freshening. So now, I have, IMO, the most perfect Mopar combo that I could ever wish for, altho it sucks quite a bit more gas than the previous iteration.. The point is this; for me, having torque from idle to 50 mph, trumps top-end power all day long.
Btw, just so you know, this 367 has gone 93 in the Eighth, so, the top-end is not exactly a slouch, lol.

For you, maybe torque is Not your priority. IDK. So then, you will have to think hard about the big picture, so that you build your combo the right way the first time ..... I'm on my Third cam now, and have run 4 different transmission ratios and just about every rear gear available, looking for the perfect Second Road-gear, for the most part. It's pretty good now

Ask me if I miss the rumble of the 292 cam...... lol.
well sur I do,
But I'm never again going to compromise my build to get a lumpy idle.
My favorite cam ever in this 367 was the 223/230/110 cam. I could hardly hear that cam, even down to 500 rpm. But man-o-man that lil sucker pulled hard at 195psi. and the bonus was, it got great fuel-economy.

Think of it this way; if your engine makes a maximum torque of one ftlb per cube, your 340 is gonna make that somewhere north of maybe 3600. Having the right second gear ratio at say 30 mph could mean the difference of rear-wheel torque of say
340 x 1.92 x 4.30= 2807 versus
340 x 2.66 x 3.10= 2807.. or
340 x 3.09 x 2.67= 2807or
340 x 1.67 x 4.94= 2807
all the same 2807, just different gears. any one of those gear combinations, will do the same job...... in Second gear.
If I had to guess, I'd guess that your 340 will really really like the 4.30s in Second gear, but it might be overkill.
And finally;
Brutal acceleration requires the tires not to spin. Yeah good luck with that and 4.30s