Ok first post! and yes I did do a search but all I found was Tracker info. I planning on buying a tin top Sammy soon for a second vehicle but would like to know if I can swap in a 2.0 J20 Aerio engine. Will the motor bolt up to the tranny or do I need an adapter plate? I have done motor swaps before on a few MR2's so I know whats involved with wiring, etc.. I thought about just putting in a G13 twin cam from a Swift, but would like alittle more power. I drive a 03 Aerio SX everyday and it's a great car/engine. Also I can buy lots of Aerio's for cheap threw the salvage auctions instead hunting down a rusty Swift gt to pull the motor out of it.

You will more than likely need an adapter to make it fit.  Thats both motor mount and trans.

The J20A was also used in the second generation Trackers & Vitaras, so you could get a transmission & t/case that will bolt right up and possibly make the swap easier.

i was thinking about doing this swap too. From what i'v read and seen the best way to go, would be with trail tough's kit. Some might say its a little pricey but if it were me id spend the $$ for it. Here's the link.

http://www.trailtough.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=18&category_id=6&option=com_virtuemart&Itemid=53

You will need some parts off the Tracker/kicker 2.0.  The Aerio cooling water outlet goes straight out the back of the motor, which would be into your firewall.  The Tracker outlet turns 90 degrees to make it parallel to the firewall.
For the install into Trouble Race Car (a Tracker) we had to get a Tracker 2.0 oil pan, and you need the pickup tube also.  You may be able to get by with the Aerio oil pan, especially if you have any lift.   I used exhaust pipe to route the cooling return from the back of the motor through the firewall, up to the front of the motor, and across to inlet on radiator.

The Aerio is more than 3 times the HP of a stock Sami, and w/o stronger running gear or a very light foot, I would plan on breaking equipment.
If you get the Aerio from an automatic tranny, the ECU will be throwing error codes for lack of communication with the transmission computer.

the other two things not mentioned is the the intake manifold is troublesome or so ive heard that there are fitment issues... and the tracker exhaust manifold is needed to make it bolt up as the aerio is transverse mounted.... are you going to run manual trans? the transmission will bolt up however the flywheel is where it changes. trail tough sells "special" flywheels to specificly run a j20a to a sidekick tranny or sammy..you could go expensive route and get everything from trail tough that makes a kit to do such a swap... hope this helps..

The Tracker exhaust is smaller, we cut and turned the bottom of the Pre-Cat to get it pointed in the correct direction.  Passenger side motor mount fits, Drivers side mount has to be fabricated.  We built ours around the pre-Cat.  If you aren't using the Pre-cat then you can use the short header and build the exhaust off it (and the ECU will throw codes.)
 
No doubt the Trail Tough kit would make things much easier.  The best thing to do is getting a motor from a vehicle that matches the drive train (Manual/Automatic)  The newer automatic ECU's throw codes without the communication from a Trans Control Unit.

It does have much more power.