[Super73]

What are you planing for intake?
What is your target weight?
What headers are you planing on running?

I think a bolt on 5.3 will make about 300-315 to the wheels with the right combo through an auto. I honestly don't think it will be enough to get you there unless you put steep gears in the rear and put the right verter in. When I say steep I mean 4.30's with 28" tall tire. Also most likely something closer to a 4k stall. But with that tire/gear, you would only be at 2,200 rpm at 65mph with the converter locked.

Now it it were me, I'd put a 220/224 cam in it with a 4,500 rpm converter and 4.56's with a 28" tall tire and and try to go 12.9x.. With that cam, you not going to loose bottom end TQ, it should have no problem keeping vacum at idle and run very well.