Ok, I cant tell exactly from the pic. But, it looks like he welded (wtf..?) the top of the mount somewhere between the two factory mounting holes.
The rear holes are for mounting I6's, but are somewhat frequently used for mounting SBC's. I thought a lot about trying to use the rear holes on my 496 project, but that is some serious work.
It looks to me like you have 73-87 SBC towers which will work just fine. There is a faq on the board about how to convert them. I'll look it up for you if you like.
I used them on my 72, and it worked, but I wasnt happy with the result at all. The motor sat a few inches too high and up at a slight angle
I've since bought the correct 72 only mounts incase I ever want to sell it.
You can get 67-71 BBC mounts and towers quite cheap.
you asked about these:
ttp://www.performanceonline.com/sto...cat=455&page=1