Straight Axles on these year frames?

[justcuz]

If you wanted to convert to a straight axle, the best way would be to find a front 4wd suspension and swap it in. Don't forget the engine mounts since you would be removing the entire front crossmember.
In 1960 Chevy went to IFS front and coil spring rear with an entirely diffierent frame. A very strong one I may add. It had torsion bars for the front suspension and an extra crossmember to accomodate them, plus a huge x brace in the chassis. I think the 60-62s frame were the strongest of that bodystyle.
59 and down had straight side rail frames with beam axles and leaf springs.
Hope this answers your questions.