Sounds like a good solid set of parts. Definitely geared toward your application of 99% street.

Which version of the EZ heads did you buy?
The stock six pack intake and carbs will be a limitation, but pretty cool looking on a street car. Not a lot of duration for 500+ CID (4.360 x 4.250 = 507.6 CID), but OK for 99% street.

Being -27 dish, -.010 below deck, it will be mild on compression ratio. The rpm issue could be many things, including valve springs, what was the actual measured pressure on the seat and open? Don't expect much power higher in the rpm band with the combo you put together. Head restricted, intake, converter stall speed, headers? etc.

I second the suggestions to start rechecking all the basics.