I believe people from both styles as well as Kumdo regularly post to this site.
Here is a link on the differences.
/viewtopic.php?t=879It appears most changes are moderate before 1st Dan. The forms are rather similar. WHGF adds Gyuk Gums 1-12 before blackbelt. I don't think those are similar to things you might have done.
My advice is to talk to an instructor from a school you are interested in.
I suspect (but it is only my guess) that ranks below blackbelt have a better chance of being honored directly (with some requirement to learn the new matieral) since the curriculums are somewhat similar, but 1st Dan and after, that may be a different story.
Good luck!