i'm looking for a used engine for my rx300 awd.....was told by some that a sienna van motor would work....can anyone here tell me for sure which engines will work? i know i will have to change pretty much everything...just need to know if the long block(head/bottom end) will interchange

 

You should do an advanced search....IIRC the 1MZ-FE motors from other vehicles are slightly different....I believe someone swapped in a highlander motor or maybe it was a tranny, but had to mod it in someway.

 

Based on this older post, some of the mounting points that are drilled into the block are different, and that is just between the RX300 FWD and AWD motors.

Link to older post