does the jdm oem LSD drop in a usdm tranny without mods?
I know the ring gear on the LSD is different than the open diff.
If Ihave the LSD with it's ring gear is it a drop in affair?

 

Might want to check the countershafts first to see if it is compatible. I spent several days trying to figure out how to put an ITR LSD into my Integra LS. I finally figured out that the countershafts AS WELL AS the ring gear had to be swapped out.

If you had an Integra/Civic I could help you out better because there are so many people doing these. However, with a Prelude....I dunno.

Perhaps you could call the parts counter of Honda and ask what the part number is for a JDM countershaft and a USDM countershaft? Can they even check JDM numbers?