I should probably mention something else;
For a streeter; the stall is chosen to get the rpm up to where the power is, as quickly as possible, so you can spinthechit outta the tires.
However, the gear ratios will, for a streeter, do much the same, easing the stall requirement.
Lets see how this works;
Lets say you had a 3.73 rear gear and a 2.45 low for a total First gear Multiplication of 9.14/ and say you had a 3000stall TC/ and say your engine makes 300 ftlbs at 3000, which by the math is 171 horsepower. This is a typical set-up. So also by the math , this equates to 171 x 9.14=1563 horsepower into the rear axles, before correction for the hydraulic ratio inside the TC itself. Lets ignore that stuff, assuming it to be the same for all these applications.
Ok now lets install the A500/2.74 First gear, and a 3.91 rear gear, for a multiplier of 10.71. But lets back the stall up to 2600. And assuming that the torque at 2600 is still 300 which translates to 149hp. The math is thus 1596 hp into the tires. Yeah I manipulated the numbers just a lil, for effect.
In the first case with an A904 your cruise rpm maths to 65= 3019 at zero-slip; could be say 3%slippage, so say 3100rpm.
In the second case 65=2180 in loc-up.
Now, what is not evident is how the 10.71 ratio will spool up a lil quicker than the 9.14 ratio. But hang on a sec, what are the Second-Gear roadgears? Well; with the A904; 3.73 x 1.45=5.40; and with the A500; 3.91 x 1.54=6.02 which is 11.5% higher and thus spools up like it had 11.5% more rear gear. This is where the realchit is; 11.5% is a lot
Cruising at less than 2180rpm with an engine with a "bit of a cam" will NOT bring fuel economy to the table in the amount that you might expect, on account of the shortage if ignition timing problems already discussed. You gotta get the cruise-vacuum up.
To do that you have three options; 1) Slam the intake valve closed sooner, or 2) start with a higher Cylinder Pressure in the first place, or 3) give the engine the ignition timing that it craves. After that you just lean it out until it melts down..... lol.
My unit cruises at 65=2240 rpm/the cranking cylinder pressure is over 180psi/and the cruise timing is up to 52 degrees. With one size smaller cam, she pulled in fuel-economy akin to a small EFI 4-cylinder.
Now, knowing all this, a case can be made for installing a smaller or less-powerful engine and gearing it accordingly, on account of, on the street, Second gear usually gets you into speeding territory anyway.
Lets take out 10% and see what happens. So now, the engine is at 270 ftlbs. and lets make it a 2800 stall, still with the 2.74 first gear, but lets give it 4.10s. The power is thus 144hp and the gearage is 11.23 for 1618 hp into the rear axles. And 65=2290rpm. and second road gear is now 6.31, up 17% from the baseline 5.40.
Lessee, 10% from a 360 engine is a 323.. or, this is about one cam size ........ I like the 360 because the longer stroke lets you get away with more stuff at lower rpms. So yeah, I took out some cam. And I might do it again.
I rest my case.
Ok not to be blindly ignorant; as the speed goes up, so does the wind resistance. Therefore all this math rapidly falls to meaningless after say 70/80 mph, and if you want to continue accelerating at the same rate, yur gonna need; more engine, more gear, or less mass. The wind is a bugger.
