Horse power guesstimations

The 346 heads that came off that motor flowed at 255 cfm @ .550 lift on my brothers sf-1020 flow bench. That is were they maxed out. The previous owner said that it had about 500 hp. I think that the engine is at least 10 years old, because the cam has ep45 cast on it and no one seems to know who makes them. The lobe measured at .370 lift, but i am not to good at engine work so who knows. I was told that the cam was a comp .562 lift 265 @.050. I'll get my brother to measure it and check the valve to piston clearance when he is finished porting the heads and manifold. It helps to have a brother with a cylinder head machine shop.
One of those desk top dyno's sounds like a lot of fun, putting together different combinations to see what you come up with. I takes some of the guess work out and could save you a lot of money.
Any guess's on et in a 3200 lb. dart, me in it. 4.30 gears 29.5-11.5-15s?
No matter what the time, i'm going to include a pair of ex.lg. depends as part of my safety gear.
Thanks again everyone. Now off to work to pay for this combo.