Lord Engine Mounts

Hope someone can guide me in the right direction on this. My engine
mount is a dynafocal for a Lycoming O-235 L2C and my project is an
experimental BushCaddy R-120. I have been looking to purchase the
rubber engine mounts. The various places I have looked, list two
different model number mounts for the same engine. For instance a
Grumman with an O-235 L2C may take a Lord Mount number J-7402-24. A
Piper with an O-235 L2C may take a Lord Mount number J-7402-16. And
there is a $30 price difference between the two. How would I know
which one I should get? Does anybody know what the significance of the
24 and the 16 in the model numbers denotes? Any rules of thumb I
should be following here??

Thanks for the help. Don....