first off the year you will be looking for is a 93 which it the first year for impreza in the states not really sure when they started making them in japan.
Second I also heard the the auto tranny handles more power then the manuel but your best bet would be to do alot a reshearch before you jump into anything.
With the motor,the 2.2 block out of a impreza is a semi closed block I belive you will be looking for a ej22t which will not be easy to find in a junk yard. You can buy the block from subaru for 1500. Just my .02.
Chris