Ford Repair: idle problem and engine swap, new gt500, vacuum lines

Question
Well, my daily driver (86 Mustang gt) idles badly.  It just wants to die soon after I start it.  Also while I am driving, it jumps really hard when I give it gas.  I was thinking it was a tranny issue but that is not they case.  I have been told it might be a vaccum leak.  I just do not know.  My next question is if it would be pausible to take a new GT500 engine and drop it in my 86.  But that is going to be a while before my wife lets me do that.

Answer
David-

  It certainly sounds like a vacuum leak to me.  A simple way to find cracks or leaks in vacuum lines is to take a can of starter fluid/carb cleaner/similar aerosol and spray it in small amounts (and I stress SMALL amounts...this stuff is flamable) around vacuum lines and connections.  If there's a leak the motor should smooth out for a second when the spray hits the leak.  As for the GT500 motor...I'm sure it's technically possible, but as of right now I'm willing to bet it would involve a ton of fabrication.  Forget the fact that I'm sure a new GT500 motor probably costs over $10K, the fabrication alone would set you back probably close to that much as well.  Then there's hood clearance issues...with the blower on it that 5.4L is a tall motor.  A cowl hood could take care of this if everything worked together, but no gaurantees.  If I were you I'd look into swapping in a 4.6L motor...maybe something from an '03-'04 Cobra.  True, it's not quite as impessive as a blown 5.4L, but it's still a blown 4.6L and I know for sure that it's been done before in Fox body Mustangs.  Hope this helps.

Steve