Recommended carb jets

Guys,
My son's '74 Duster stock 318 has an Edelbrock 1406 600cfm straight out of the box (on a Weiand 8022 intake), and it runs OK, but tends to bog at times, or when you crowd it a little....like it's not getting enough gas. We also have an Edelbrock electric pump and regulator installed (set at 4.5 to 5).

I wanted to up the jets a bit, to give it more oomph, but not go too far overboard...since I'm not a carb guy, I thought I'd ask for some advice from those of you who have done this upgrade.

Thanks,
Rob