Can you put a newer like around 2005 engine in an old 1999 Forester without too much trouble? How much wiring/ plugs difference is there. The forester is an Auto Trans. Thanks!

Can do up to about 04-05 N/A engine no prob.

 

In either 05 orn06 the heads changed and got active valve control, those engines will be a no-go into a 99.

up to 2004

 

2005+ has active valves but you can still use one, it just won't use the active valve stuff.  swap the intake manifold from your car onto the new block.

and it's 2005+ that are drive by wire right - so swap your throttle body and route your throttle cable.

 

or bolt your 99 heads onto the 2005+ short block.

This is great info folks! Thanks so much. I just bought a near perfect 99 Forester with rod through the top of engine for $200! So gonna be looking for cost effective engine to put in there. I will pull the current engine soon and see how the heads and all that are. This babe had no rust, working air, great tires, great interior, no dents at all... Think I will do it right and drive it for a while. Even has a trailer hitch! 3 Subies in the drive now.... 81...98...99. :-)