I can relate to the "you are nuts for leaving the solid axle in the truck"
I say no, not crazy.
I had a Mustang ll in my 46 Chevy truck with a 350/350. The power rack was too twitchy at speed (yes, there is a fix for that) and it was just too wimpy for a "TRUCK" truck. Its great if the wood in the bed is varnished and you just drive it as a car, then its fine, but as a TRUCK, its too wimpy.
I know, everybody wants to clip it with this and that, truth is, that is one solid unit and its good.
That is what I was thinking with your comment on "NOT BOXING THE FRAME". (that is to say, when I am not thinking about boxing it!!)
The frames in these, especially with the solid front and rear axles has to move, flex and twist. That is why the cross members are rivited in, to allow movement. I have seen boxed frames that will crack and crack badly at certain stress joints. Backyard engineering (which I am good at!) gone bad.
Well, thats what I think, love to hear any arguments, as I will need to change my mind several times before my project is finished, if you know what I mean.
Your 3" dropped axle, did you get the steering arms dropped as well?
How much was it?
Where did you get it?
Do you have any pics of it?
Am I asking enough questions?