OOOOOH Boy!
I feel another REAL vs Replica argument brewing.
As I recall wern't the ZL1 motors introduced in '69 and wern't they 427's rated at 550 hp but rumored to be more like 600 hp.
So it seems to me that a 510 hp 454 zl1 is not a real ZL1 but a fake, copy, replica motor and also not as good
also isn't Chevy making a 500 something cube crate motor w/720 hp?
seems to me like that would be the GRANDADDY chevy crate motor .
anyway as I am learning the hard way Ford FE motors are way more expensive to build up than Chevys and that simply comes down to supply and demand.
Have a good one,
Dan