The spring mounts in the front, and the shackles on the back of the springs (in the firewall area) are mounted directly to the stock chassis rails.
My buddy trimmed the K-member a little to slide them back as far as possible so as to center the wheels in the wheelwell as much as possible.
The frame rails are pretty straight, and there was no need to make a rectangle, steel frame stub. I guess if you were putting a big block in there, it might would make life a little easier with a frame stub, but you would have to do a lot of work to line up all the front sheetmetal again... unless you welded it all together and made a tilt, front end out of it.
I should get over to his shop this week...I'll charge up the battery in the camera, and get some detail shots...It's all just tacked together right now while we work out the steering.