My answer, if you can call it that, is for a streeter on street tires, with street suspension..
I was in the same 350/400hp pickle.
What are you using the car for?
In a straight-line;
I went from 245s to 255s to 275s to 295s, and finally to 325s..... and , the tires never stopped spinning; to 80mph and beyond.
In the turns;
with 275s or less, the back-end would step out and spin me around at the slightest provocation.
In first gear;
With a stout-360, there is not much you can do, short of detuning the engine to soften the hit to the tires, or
Up-tuning so you can control it better. A stout 360 will make about 430 to 450 ftlbs, which is like a 440Magnum of the 60s; that's a lotta torque, and it comes in fairly early.
So for me, First gear at WOT, is just a way to get into second.
Your tuning tools, with an existing combo,are; TC (Torque Convertor)Stall, carb type and size, and ignition timing. You just have to either; A) learn to feather the throttle, or B) make the engine lazy, or C) some combination of A and B.
In first gear, traction with a 360 is a joke.
But first gear will never be good for anything else.
So I geared my car to put second where I needed it to be.
But if I had money, I would have put it into two things; A) a traction-aid, and B) suspension
Unfortunately, the suspension changes required for weight transfer, to better your traction, very quickly take the car out of the realm of streeter.
That just leaves a traction aid.
But here's the thing; your 60ft is likely gonna change only a lil,say about .4 second at the best; and up here I would have to spend in the neighborhood of $3000 smackers, including the biggest tires you can fit in your stock tubs, on custom wheels. Your zero to 60mph might improve .5 or .6 second.
To me, it wasn't worth the coin.
Instead, I fabricated a throttle stager with a coathanger and a couple of springs, for my 750DP carb. It has a soft spring on the first part, and a stiffer one on the second part, so I can always feel it. I made it adjustable, so the first step just gets me 65/68mph. The bonus is this makes a great cruise control.
Then I just learned to drive the beotch.
