HEMI differences

I have a 3 year plan to get a HEMI into my 68 coronet to replace the 440 and I see Jegs and summit have the crate HEMIs

my question is: what is the difference between the 426, 472, and 528 as far as dimensions ......do they all interchange stuff like valve covers intake manifolds and items as such??

Motor mounts: Are there mounts available to bolt up to a 440 K-frame?

flywheel: do the crate motors take the standard 6 bolt flywheel??

Anyone have experience with the mopar performance HEMI engines?