Too much engine work at once

With; 3.55s, a 2.66 low, and 26.5 tires, the doughiness will have rolled off by about 26mph, unless you pick the 268/110cam, or if you have a 318, then you can expect the doughiness to last a bit longer.

Here's a stock 318, ICA of 48*
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 7.10:1 .
Your dynamic cranking pressure is 136.77 PSI.
V/P (Volume to Pressure Index) is 114.............................................. 114 ..

And here it is with a 268 cam, ICA of 60*
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 6.62:1 .
Your dynamic cranking pressure is 124.66 PSI.
V/P (Volume to Pressure Index) is 96.................................................. 96 ..
Notice the drop in cylinder pressure from 137 to 125. That's 9% or about the equivalent of 1 rear gear size. So you will need 3.87s to have the same low-rpm/ low-speed performance, after the cam as before.

But here is the same 268/110 cam now at 10/1
Static compression ratio of 10:1.
Your dynamic compression ratio is 8.22:1 .
Your dynamic cranking pressure is 165.61 PSI.
V/P (Volume to Pressure Index) is 127............................................... 127 ..

Notice the pressure is now up to 166, or plus 21% over stock, and plus 32% over the doughy 8:1/268cam . What this means to you is that the hi-compression engine will need just 2.94s to be on a par with the doughy engine and 3.87s When operating in the low-rpm,low-speed mode, that rolls off at about 3000/3500
Well, it doesn't mean that exactly, but that's the best way IMO to illustrate this.

What it really means is, that with the same 3.55s;
the 10:1-268* will go like a raped ape, and
the 8:1-stocker you know what that one does, and
the 8:1-268* will be less powerful in the doughy zone, and won't wake up until between 3000/3500 as it climbs towards the torque peak.
Now,in a stick-car, the engine is married to the rear gear......so with the Lo-C-268 you will be stuck in doughy-land from idle to 25mph,any time the tires are NOT spinning, if they will even spin, then the power will come in, and if you keep the Rs up it will be so-so/pretty good. But, whenever you are in second gear at low rpms, say below 30/35mph and you want to accelerate briskly, well you can't because you are in doughy-land. So you are forced to downshift. I tell you what, all this downshifting/upshifting gets old in a hurry. My solution for me was 3.91s........ or better,lol.Then you can just leave it in second from 30/35 to 60/65 mph. And the bonus is with a 10.40 starter gear, the teener stands a chance of spinning; I mean a VP of 96 is like getting down to slanty territory.
Anyway, I'm just trying to make you aware of the road you are taking, that I for one will never go down again.
And finally, the 268 is about the biggest cam a teener owner might install. There are several smaller cams to choose from, with less doughiness resulting.I just wanted to paint the ugliest picture I could, with the biggest shock-value.
From the 240 stocker to the 268 is about 4 cam sizes, so you have less radical choices.
And double-finally; consider the price difference from pulling the compression up, to installing 3.91s
If you have a 360, things are only slightly better, because of the inherent extra torque of the bigger engine,specifically the longer stroke. And again, I for one, will never travel down that low-compression up-cam road again.

Happy HotRodding