Are you asking wether or not there is a different firewall for slant six cars? If that is the question the answer is no. The only choice for firewall was AC or no AC.Yes, that was what I was wanting to know, of all firewalls had the bulge at the 1:30 position. Thanks for clearing that up.
The picture you posted looks like a slant k to me. If it isn't that is a very very tall left mount perch for a v engine. Another giveaway is the coil low on the passenger fender right above where a slant dizzy would be. That coil location is a long way from a small block dizzy, but not too far from a big block.
Yes, it definitely is a /6 car, as the pic is a member's resto project here on the forum.