I got these two wheel chair motors for a large scale tank-like application. the two motors are Invacare wheelchair motors or merits dynamic wheelchair motors. The two are practically the exact same. Part no. WMT90423 (Model M6).

Now, my question is: can I remove the drive shaft? I know that this is a one-in-a-million shot, but If anyone has any experience with these motors it would be greatly appreciated for your help. I am wanting to remove the drive shaft and replace it with another shaft because the ones that the motors come with are about 2" too short. Another option I suppose is to just weld 2" onto it, but I don't know how much stress that would withstand. So, if you have any suggestions with this, your knowledge is greatly appreciate. Thanks
Mitch