I've got a 12a for sale, the car was an automatic, and people keep telling me that they can't use the engine because they have manual tranny's...

Is there really a difference between the engine in a manual and automatic car?

i would think you could just swap the flexplate for a flywheel, and bolt up the 5 speed

 

You are correct. Just need to remove the rear couterweight/flexplate and put on the flywheel/clutch and pilot bearing. I put an auto engine in my old manual SA, and it worked just fine.

Some of the rats nest stuff is a bit different on the autos (people may want more of a plug-n-play, but they can always swap over their old emisisons stuff if they need it.

 

If the new buyer wants to use a lightweight flywheel, the automatic is actually an advantage. Most of the lightweight flywheel setups bolt to the auto trans balance weight to maintain proper balance in the rotating assembly. If they start with your ATX engine, they can save the cost of the balance weight.