Wondering about installing an earlier model EJ25 into a '99 Legacy. Hollander (car-part.com) says only '99 interchanges with '99, I'm just wondering what the physical differences are. A cursory search indicates the earlier ones have a 4-bolt bellhousing vs. 8-bolt, requiring mounting up the starter a little differently-- is that all?

Other than bell housing it should work just fine.

The 99 is better though. The 99 2.5D uses a phase2 block. So it has the upgraded bearings and the thrust bearing moved to 5. It's a much better bottom end.

But the earlier ones will work fine.