Husqvarna 51 piston ring issues

[Sksaha]

I decided to look into the 51 I bought used years ago. I was never able to start it. Checked compressed, barely 50. Removed the cylinder and the ring was worn and a piece was broken off. There is some surface scratch in the cylinder wall that will hopefully polish off. I am having a hard time finding the correct size piston ring. Specs says I need a 45mm ring but the cylinder bore is 46mm indicating possibly (?) a 55 head. 
Do I need a 46mm piston or a 47mm?
Cylinder is a Mahle 46ZD5. Also will appreciate OEM or good after market part #.
I just want to get it running and just sell it. Thanks

[Spike60]

Yeah, it looks like you have yourself a 55 top end on there; 46mm. Ya never know with old saws what surprises someone else has left you. Husky apparently doesn't like to sell pistons, because the piston and complete top end are priced the same $99.99. Seeing the glass as half full, you could say they are giving you a free cylinder with the piston?  :laugh:  Here's some part numbers for you, which should cross over to AM if needed. 

ring--503289014
piston--503608171
cylinder kit--503609171