Highest LIft cam with 68 340 with stock intake and carb

Here's what I mean; the specs on that cam are 273/276/110/106 and 56* overlap.
>plugging the numbers into the Wallace calculator, assuming a true Scr of 10.8, this nets a Dcr of 8.7@178psi and a VP of144. That's a nice safe place to be. With the aluminum heads and tightQ you could run 87E10 with the right tune.
>Now suppose we swap in the popular 268/276/110/106/and 52* overlap. The logs will still choke the overlap cycle, but now, still with a 10.8Scr, the Dcr rises to 8.86@182psi and the VP to 151. I have run 8.86 on 87E10, so I think this is still fair game as to Dcr.
>Now suppose we dropped another cam size and reduced the LSA to 106 for the 4 speed. Still with 10.8, the Dcr now rises to 9.0@187psi and the VP to 158! And the overlap dropped to 52*. I have run over 187psi on 87E10, so we're still on pumpgas. Of course the logs are still choking the overlap.
So in each of these cases, as to lower rpm torque production, less is more. and because of the choke, very little top-end power will be lost. Also with each size smaller cam, the power extraction period gets longer, and that usually means better fuel economy at part throttle.Also each smaller size cam is bring the power peak down to a more useable rpm, making the midrange a happier place to be.
Now, on all of them, the choked overlap is choking the power production upstairs say beginning around 4000 and reducing the power little by little-more from there to your shift rpm.

In my previous combo;a 367 4 speed, I was running 10.9/8.9/@184psi and a VP of 162, and I can assure you that at a VP of 158 will have a tremendous bottom-end.I think it must be 7000 ft lbs or more,lol; that's an exaggeration ok.

Ok but the cam is staying, so then we run with the choked overlap. So like you, I'm wondering how much power is being lost? IDK. And does it really matter to you? Probably not , cuz you're a streeter with a 10.40 starter gear. And the combo spins to at least, I'm guessing,50 mph AS IS. So roughly 85% of the time, you already have more power than the chassis can handle! lol.
So that's why I say; make it hook first. Then headers. Then you can fool around with intakes and such.
But if you really want to install a different intake and carb, go ahead. But it will just spin the tires exactly the same as it does now, and you will not go one mile an hour faster from zero to 60 lol, nor one second quicker; not until it hooks and not up to it's true potential, until the headers go on. It's kindof like putting your socks on after your feet are already in your shoes. Namely certain things have to be done in a certain order.
Anyways that's my 2 cents worth.
BTW; nice cam. I'd make that one earn it's keep. If I had it in my 367, the AG and 750DP would finally come alive: 243@ .050 is sweet, just not with a FTH of 292/108 lol.