NAT Overload both directions

I am trying to do NAT overload both directions between two locations in
my company.

One location being inside and one being outside.

I can do the overload on the ethernet interface going from inside to
outside.

I seem to have to use a pool to go from outside to inside.
When I set this up I wanted to hide everything behind a single IP
address pool, but seems it only lets one client on the outside to use a
single IP in the pool at a time and not do PAT.

I thought I had this working in another location I used to work at but
been a while and can not remember.

Is this possible ? another way to do it ?
Can I have two interfaces be inside and overload between them ?

Any sugestions would be greatful.

Thanks.
MC