The G3 newborns are reasonably close to a similar size to the G1 babies - its just that their heads are a little [!] out of proportion.
The only picture I have showing lots of G3 newborns is one of them in the G1 Lullabye Nursery and in various G1 baby accessories...alas the picture does not belong to me so I dont really want to post it unfortunately....
Hopefully someone else will come along and help.