My question is will a dash cluster out of a legnum or galant fit a 3rd gen Magna ?

Nope. Different shape, and different harnesses and plugs if I'm not mistaken

From what I've seen the shape is the same, going from google images , even the shape and layout of the gauges looks the same

Only reason I ask is cause a place in Europe make nice looking plasma gauges for the galant and they look identical to the 3rd gen Magna cluster.

Completely different

Really? They look exactly the same

I've got both a Verada with the LED display & a Legnum with same style LED display - they look the same but totally different.
Different size, shape & harness.

Well there ya go.