there are 2 ways to attach the cones to the frame. I cut a small strip of 1" flat stock, drilled a hole in it, layed it on top of the frame above wher the cone is, (be carefull brake line on drivers side might get in the way..) and put a washer and bolt up through the cone. the hardest part and it wasnt really hard at all was getting my huge softball size hands up above the spring perch to put the nut on the bolt ....but its very doable. 30 mins done (ok took over an hour to come up with the idea....but I'm slow minded)

the second way is to drill hole in flange of black cone and drill and tap frame. I read about this idea long after I had done mine.

both ideas would work just fine. I never had any trouble with the cone coming loose or the spring popping again. drove it for thousands of miles ...no issues. then I went to a longer spring (more lift) and left the cones attached to frame.
hope this helps
Dave