craftsman lt2000 hydromatic

I just picked up this 2013 LT2000. It runs well, cuts fair, has some slop in the steering & the brake goes from nothing to ejecting you from the seat. The mower deck is out of level & cuts too low. I am excited.

Will a 12.5 engine work out good in place of an 18.5 on a 42" LT2000 The 18.5 is shot and I got the mower for free and had a 12.5 laying around. any feedback would be great. Thanks.