aluminium head questions

Alright, here's what I'm going w/:

MP 5153524 heads CNC ported
Edelbrock Performer RPM intake (they don't make an air gap for a big block do they?)
750 cfm carb (I'll take any advice here)
Hyd roller cam (probably XR274HR... 224/230 duration at .050", .574/.570 lift w/ 1.6 rockers)

What's the length difference in flat vs hyd lifters? Will I have to change pushrods?

Feel free to shoot holes in my proposed setup.