wanted info on aluminum case OD trans

I have a van/truck overdrive in my roadrunner.Makes cruisin great ,I just don't know if I'd throw any horsepower at it.The horror stories I've heard are ,floating countershaft,deflection from a weak aluminum case.and horrible spread in gear ratios.I have a very mild small block and occasionally beat on It.
As far as I know the ratios are
3.09 1st
1.77 2nd
1.00 3rd
.72 O.D.

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