[mrbacklash]

I know there are differences in the mounting brackets most notably the 317 has the retaining pins on the frame and the 318 has holes on the frame for the arms. would it be possible to use bolts and nylocks the mount it to the 318 while i look for the right mount?

 

[KB]

I believe the arms are different lengths on the two models listed

 

[shadetree]

And certainly the width between the two arms is different.

 

[hankvc]

On the 50" mower deck, the draft arms for the 318 are different from those for the 317. Those arms are on a shaft, so changing the arms on the shell should be all you need to do.

PC1959 is the parts catalog for the 50" mowers for 314 and 317, as well as the later open-frame 300's and 420/430. That will help you identify configuration differences.