i dont know about the two engines mounting up the same without hassles but i do know i am rebuilding a 1.6 16v engine for my tracker because its getting a little tired and if it were me i would definetly go for the rebuild. u never know what ur getting when u buy used and when u buy new its so expensive, if your mechanically enclined and have the time i would rebuild it yourself and know what u got under the hood.
ps. pay the extra penny for a machine shop to do the head [new valve seals , recut and check for warpage it will save u alot down the road. just my opinion.