If I'm not mistaken, the 2.4 liter engine is the 2000 Camry engine...... I could be wrong, but I do believe that's it. (Looks the same for sure, having traded in a 2000 Camry for our first xB..... popped both hoods and took a look,..... VERY NEARLY the same shape and size and all..... only a few things different, but mostly cosmetic and power steering stuff.
I do like the OD transmission idea though. Don't know if putting more engine in would change a thing...... unless you are looking for an xB GT.