64 bit processor what is the size of ptr and size of int

size of ptr is 64 bits. As Address bus is of 64 bit  2power64 size of memory can be accessed directly..
while in 32 bit 2 power 32 i.e 4 GB memory can be addressed RAM physical memory ant go beyond more than 4 GB
Size of int depends on the implementation generally its 32 bit as in
OS ------------------Data Model-----shor-t------int-------long----longlong-----ptr

Window--------------LLP64----------16---------32------32-------64----------64
Linux-----------------LP4-------------16---------32------64-------64----------64
SPARC--------------ILP64-----------16---------64------64-------64----------64
--------------------------------------------------------------------------------------------

What should be taken care while porting from 32  to 64 Arch?
If client is in 32 and server is in 64 bit what care should be taken?
--padding , ediannesss,pointers ?