As far as I know, the OFR will pretty much be like a direct replacement for the JT580LP you've got there. However, you may have to do some slight alterations to make it play smoothly. A guy I talked to who put an OFR in his DK2, said that the tremolo route was just a hair too narrow, so the sustain block of the OFR was scraping lightly against the side of the trem route. He just brought out a file and took off enough wood so it cleared, and now it operates perfectly.
You will have to replace the bushings for the trem posts though. I believe the JT580 posts and the OFR ones have different threads on them. Once you've gotten the old bushings out, you'll have to pound the new ones in with a rubber mallet or something, because the OFR bushings are slightly wider than the original ones. Shouldn't be a problem, but be careful so you don't pound them through the wood - I've been told it's pretty thin wood in the back there.
'bane