I have recently purchased a dune buggy, which supposedly has a YZ490 motor in it, but how do I tell what model and what year for sure ?

I replaced the "cover, crankcase 3", but this fits 6 different models:

IT465J, IT490K, IT490L, YZ465H, YZ490J and YZ490K

The engine block has a part number on it - 23X-000354, but this doesnt match anything.

I need to replace the ignition coil, but there are different part numbers for each of the above.

There is a Mitsubishi part number on the coil - F6T411.

Any ideas would be appreciated ?