If you’re talking about the P60s, there’s a couple of models on 3dcontentecentral:
http://www.3dcontentcentral.com/download-model.aspx?catalogid=171&id=208143
http://www.3dcontentcentral.com/download-model.aspx?catalogid=171&id=171413
The only difference between the reductions is the lengths, which you can from this datasheet:
http://banebots.com/docs/P60A-DATASHEET.pdf
In Autodesk Inventor, you can use Thicken/Offset to make the necessary changes, not sure what the appropriate tool would be in other packages.
–Ryan