Hey 77Superboat, welcome.
I've heard that the World Products blocks are a little beefier. With regard to crate motors, I would make sure it is bluprinted (deck & bore) as well as check the balance & tolerances (we covered the whole crate motor debate under "502 vs ?" in the Blower Motors section).
I'm not an engine builder- Ponponracing or Racing Ray may be able to help you out with the pros & cons.
If it were me, I would lean toward the World Products- the builder could help with the warranty and dyno info. I think they're even buiding up a WP540 in this months Hot Boat for John's Ultra Shadow project.
Happy boating!
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