3:54 vs 4:10 with a low deck 499

You will have lower piston speeds with the 3.54 gearing, especially with the (?)4"(?) Stroke you will be running. I think that is something you may want to consider.

You are going to have more than enough torque with that B block in an A body that getting off the line won't be a problem.

Personally, I would go with a 470 build. It gives lower piston speeds, and greater compression height on the pistons which hypothetically should get you a longer engine life. The shorter stroke allows higher rpm's and you can take advantage of the 4.10 gearing just a little better.

Double check all of this with a calculator. Talk to @AJ/FormS about gearing and your trans ratios and tire sizes et cetera.