I would guess 600-625 hp, low to mid 600's for tq. for your combo.

Might be that intake. Just more food for thought,
I built a 506 very similar to yours, but slightly milder.
10.25:1 comp
E-heads with valve job touched up
Straightline hyd. flat tappet 240/250 .540/.530 lift, 112 lobe sep.
Edelbrock Performer RPM intake
Out of the box Demon 850 carb w/1" open spacer.
Also on a conservative dyno, this thing made 577 hp and 644 tq. Had approx. .038 quench, so it liked timing at 35.
This has to be one of the best bang for the buck street engines I did so far.
It did pick up 8 hp with the open spacer, messed around with 2", 4 hole, open, etc., it liked the 1"open the best.
So it just may be a matter of messing around with different intake combo's.