I have heard that the C5 rears are stronger then the C6 rears, is there any facts to this?

I own and have read cover to cover the C6 launch book by Phil Berg and he mentions that GM substantially strengthened the rear end on the C6 to withstand the higher output of the then new LS2.

"The differential is also one of the few in the GM lineup that is a combination of aluminum and cast iron case. Inside the differntial, the ring and pinion gears for all 2005 Corvettes are double shot peened, a technique that strenghens the metal and ensures that the gears will handle the increased torque of the LS2 engine. Previously, this process was done on the C5 Corvette only for the LS6-equipped Z06 model." (page 78)

Hope that helped.

I thought that the pumkin of the 2005 c6 was the weak one?

I update myself, I wrote LS2 when I should have wrote LS3.