Motorcycle Repair: Changing parts affecting title, cracked cases, mso

Question
I have a 1984 Harley WG with a 1340 Shovelhead.  I've got cracked cases that I need to replace.  However, I was told that If I replace them with aftermarket cases then it will change the title on my bike so that it is no longer a Harley title.  I was also told that if I find used Harley cases for my Shovel then it will maintain the Harley title but the numbers will not match, thus also affecting my title in some way. I was also told that if I did purchase used cases from somewhere that I would need paperwork to go with it such as a title or M.S.O. (what is an M.S.O.).  This has been my problem.  Most parts don't come with a title or paperwork!  How do I get the parts I need without having a problem at the DMV?  Also, how exactly does changing out the cases on my bike affect the title?

Answer
Where is the case cracked? I could probably fix it for you.
The questions you are asking are going to depend on your state. So you need to check with them.
The mso is mos. Manufacture orgin of title. Its the paper work that goes witht he cases for the title
Good luck and happy riding
Mike