I hate this to be my first post...
However, from what I have seen with many home builders quality of welding a well designed bolt on kit will have just as much strength as anything welded on.
The design of the kit has more impact on strength than the way that it is attached to the frame. I dealt mostly with late 70's ford's when I was in that phase of my life it seemed to me that all of the bracketry was bolted on. From the radius arm mounts to the coil cups and even the rear brackets were riveted on.
I think that even now much of the solid axle mounts from the factory bolted on to a frame that they could make either 4wd or 2wd
Love the forum but just wanted to put my 2 cents out there!