Chainsaw Repair

so i have this husky 50 sitting here and it needs a piston. was figuring on putting a stock piston back in as the cylinder is still near perfect and the rest of the saw is in fairly good shape save for the brake handle and clutch shoes.
the saw runs (albeit rattles like a can full of rocks) good, will cut well and still has good power. the piston is WAY WAY worn out, but the engine will still blow 155psi all day long just makes alot of slap slap slap sounds when running.
the person i bought it off of for parts said the crank was bad. when i tore it down i found the piston ovaled nearly 18thou and with a good belly half way up the skirts
i "think" it's a45mm'er but the vern. caliper i'm using says i'm just shy of 45mm buy about 1/3 a mm at just above the pin.
of course the piston and cylinder are at home. so i can't check until tonight. same for the serial#.
was bought new in 1989, has that horrible squish the filter to choke mechanism......
sooo, what other top ends will fit on this saw. part numbers would be fantastic! thanks.