I have a big problem with shaking of the engine and car. I think the problem is with balancer. I have a Mustang 65 with 302 engine, 2MA crankshaft and 289 balancer.
I want to replace balancer, but i don't know which one would be ideal fit? Inner or outter and excatly which one?

 

I have a 3 speed manual gearbox...

 

The shake could be from the flywheel or clutch not being right.

The 289 balancer is offset weighted the same as the 302, but the 302 has more overall weight. You can notice a difference in how quickly the motor revs to some degree but the balance is the same.

 

This is what i have now:
- Crankshaft : 2M A
- Engine block: C8OE 6015 A
- Balancer: C5AE 6316 A2

I think the balancer is not ok, so i want to replace it with the right one for 302.

 

Well, pully alignment may become an issue, and the 302 used a 4 bolt lower pulley.
You have a pre 5.0 302 with a 28 OZ imbalance. Both the 289 and 302 were 28oz Imbalance with the difference being the overall mass of the unit. The 302 used the thicker unit from what I guess is an evolution from the 289HP units that used more mass to help at higher revs.

FWIW I have the same engine. It came in the car looking like a 302 and I am going through the process of changing it over to "look" like a 289 from 65, I even changed the balancer over. So I ended up needing to locate alternator brackets, pulleys, a 289 water pump, a 289 harmonic balancer etc.. just to make it "Look" correct.

 

C6ZE-6380-A is my flywheel number. Could this be a problem with my balancer combination?

 

Well, that looks to be a 66 flywheel.

Im curious now, Does the car shake in neutral or just going down the road?

 

Car shakes in neutral too, but not that much. The faster it goes, more it shakes. WHen i hit 50 or 60 mph, it shakes quite a lot, so i don't want to go faster.

 

Check the fan, motor mounts and U-joints, I have had a U-joint render my rear view useless.. From the info you have given me the balancer and flywheel are 28oz imbalance and are not the issue. IT is possible that the balancer has slipped and is now off center but the 289 balancer was weighted inside the ring, and not on the outer portion, so I doubt it would change much.