Looks like it had suffered a damaged quarter, with new paint, but they didn't replace the Di-Noc. It's likely it had either a 400SBC or 454 BBC.
The 400 V8 was the standard engine for Caprice Estate in '73. Pretty sure it only got the front fender emblem with the optional 454 V8.
I think you're right, I've seen sedans with the 400 emblem (although I can't remember if they were early '70s or not), but not the wagons.