I tried to open saves in Fallout 1 with first versions of my editor, it fails. But I didn't try to find out what cause errors. I will try it now.
However even if save.dat from FO1 will be like FO2, some others formats will not. For example: http://falloutmods.wikia.com/wiki/DAT_file_format
I will try to make version for FO1 and post on NMA if success.