[CentOS] mismatch in openssh latest rpm available at centos

Hello Group,

The latest rpm in openssh is 5.8, however, the corresponding latest rpm available in centos 5.7 is only

openssh-4.3p2-72.el5_6.3.x86_64.rpm

and in 6.0 centos is

openssh-5.3p1-20.el6.x86_64.rpm

I have following questions.

1. I want to start from src.rpm and where can I get the src.rpm for openssh-5.3p1-20.el6.x86_64.rpm.

2. Can I install openssh-5.3p1-20.el6.x86_64.rpm SAFELY with 5.7 centos without causing any problems.

3. Which of these two rpms will be most compatible with latest openssh rpm version 5.8.

Please let me know. It is important for my work.

Any help will be greatly appreciated.