Would like to get some more oomph from my 318

Running the 2.74 low-gear is no problem at all, so long as the engine is set up for the powerband they require.
Say you put a cam in there that power-peaks around 5000.And you want to run the 2.74-1.54-1.00 ratio. The splits are 56% and 65%. It's a streeter so let's only care about the 1-2 split.
First gear cannot go to 65 mph, with 3.55s and 25.5 tires.That would be 8346rpm in 2.74. In 1.54 2nd it would be 4691. So lets gear it to hit 65 at 5400 ;400 over peak, in second. This will get the most out of the teener, she can give.Well doing the math, this means 2.30 rear gear. So there is no optimizing this 2.74 to show well at zero to 65. But it's ok, the 2.45 low will need 2.57s , so there's no optimizing that either.
But let's go with your idea of 3.55s and a 2.74 low. With these numbers, 65 will be 4691 in 2nd.So now it looks like a pretty good deal. It would have been better to topout at 300 to 400 over the 5000 peak but 309 under isn't so bad. That is until you meet the guy who does peak out at 5300/5400.He will pull right on by you.
Easy solution right? 3.73s will get you 4928. You see where this is going right? The right gear is actually 4.10s: which will get you 5417rpm, in 1.54-2nd. We're done right? Not so fast.We still have to work with the 56% 1-2 split.
-Ok to center the powerband at 5000 with this split, will require a shift rpm of 6400, to drop in at 3584, for a powerband of 2816,centered at 4992,close enough.So to optimize this combo requires 4.10s, and superwide powerband of 2816 rpm and a 1-2 shift at 6400 with a medium sized cam to peak at 5000rpm. and a TC at about 3584 stall.Do you see the difficulty this presents to a streeter?It's gonna need quite a cam and quite a top end.
-Lets work it out for the close ratio 2.45-1.45-1.00 tranny.We'll keep everything else the same. So now the 1-2 shift can occur at 6200, to drop in at 3658, for a powerband of 2542, centered at 4929,close enough.
The powerband requirement is 274 rpm less. This means you can tighten up the LDA and make a few more ponies, to go quicker on the same 4.10s and now shifting 200 rpm lower.The penalty, to be fair is the loss of 11.8% ratio at the line, which might be made up in the now 3658 TC requirement. If not then surely by the tighter LDA.But honestly very few times as a streeter does one need more than 4.1 x 2.45 =10.05 starter gear, with a 3600 TC.
-But here's the best part; When you kick it down at 35mph into 2.45 first, the Rs will be 4641, while with the 2.74 first it would be 5190, almost 200 rpm past the rpm of peak power. Cruise rpm in second at 35 would obviously also be lower.
-But here's the catch. The cam I picked, peaks at 5000, right? If you pick a smaller cam, every thing changes; ev-reee-thing. Everything except the ratio of the powerbands. The wide-ratio tranny will always require a wider LDA cam, to cover the wider powerband requirement.
-There is only one way around this; to make Zero to 65 just one gear.Then it don't matter a hoot what the splits are. Unfortunately to go 65 @5400 requires an overall gear ratio of 6.294, Which would require a huge amount of crank-torque to pull from a standstill, with either low gear ratio. This is not NA street-teener territory. But if you are willing to put a 6000 rpm of peak power cam in there, and hit 65 @6400, then the overall ratio goes to 7.46. This is doable with 2.45 x 3.04s or 2.74 x 2.72s. Yer still not gonna show well with a 3600TC. So to conclude, a teener needs two gears to hit 65, and show well. So back to the 4.10s