I think it best to use 2 aftermarket halves sold together, otherwise stick with OEM. I just wouldn't want there to be any misalignment on the machined surfaces between to different case halves. If one bearing pocket was mangled, could the other have been stressed? My farmertec 660 is still going, but only 50ish tanks run through it I'd guess if even that many. Who knows, maybe 100 being the gas guzzler it is.
You just have to make sure to thoroughly clean any metal dust and grit off the new halves if they are cheap aftermarket, and smooth any sharp edges that contact things like the oil line.