Welcome to the forums.
The castor blocks from FLM are very strong. Even if they do break, FLM has a great warrenty and you'll get another set for very cheap, if you even do break them. I'd suggest hinge pins from Lunsford racing. You can get a set here:
http://www.lunsfordracing.com/mm5/me...Code=TRUC-TRST
I am sure you can get them from Tower Hobbies as well.