[mcnallym]

If you have an overlapping IP scheme then how can you only need to do a Src NAT as surely the destination packet would be a local IP address.

If the other end is a 3rd party and is already NATting the destination for you to there internal that overlaps with you, then you are communicating with a non-overlap as you talk to there NAT address.

If however you only need to do a src nat then you do the same as any other NAT.

Define a new network address the same size but different subnet as your internal network.

Src = internal_net
Dst = Remote_VPN_Net

xlatesrc = S(new_net)
Dst = Original

This will nat 1 to 1 from the internal net to the new network range.