I used an Auto Rust Technicians cap (I believe those are the Safe-T-Caps you are referring to) on the back half of the drivers front frame rail on my Cuda. It fit well and has held up fine for about 10 years now, and I have no complaints.

However, after getting the cap from them, I realized it was just 3 pieces of steel welded together to make the cap, and that it was something I could have fabricated myself for about 10 percent of what they charged. I have since made my own caps for the two rear spring hangers out of some steel stock that I had on hand, and they are easily as strong as anything someone could sell to me, but it did take some time to do the fabrication. If you have more time than money - make your own, but if you have more money than time - buy them pre made.

The K frame section of the frame might be something that you would want to buy, though - depends on your fabricating skills. I'm not sure if the caps are good for this area, or if you would be better off getting a new front frame rail, or a section of a frame rail to splice in. But if you're a good fabricator, I would think this section could be fabbed up also.