I've built several that have made over 700 NA on pump 92, but those are'nt Edelbrock head motors you're going to go drive 80 miles at a clip to a car show etc with.

The Last 416 INDY motor I did on pump gas made 680 with a roller.

Last Edelbrock head real "street/daily driver" type motor I did was a 408 with Stage 2 E heads & a mild 250 @ .050" Hydraulic roller with Edelbrock EFI....that is probably only a 450 HP motor...but will run mid 11's in an E body & be able to drive cross country.

600 With Ported E heads is certainly possible especially on a normal dyno, but will require alot of camshaft to do it. ie. it won't be very street friendly, hard on parts, & require a ton of converter to work.......We just made 610HP on Rider's stingy pump with an unported 1977 W2 head last week @ 367 inches.... all it takes is lot's 'O Cam (& RPM in that one's case)

But I think better question to be asking is how much car weight & how fast you want it to go, dyno #'s are just #'s.....it's a tuning tool, not a definitive # maker. I talk to guys all the time, that tell me they want to do a "600HP motor"..... & then I come to find out they have a typical 3200-3300 lb A body & would be plenty happy running Mid 11's with it..... Well it takes About 450 HP or less (depending on car & overall chassis combo) to do that..... so I always try to get them away from asking for raw power #'s. & get down to what really matters.