Welcome. The fact that you have a ‘61 will present you with several problems. You have a torsion bar suspension. You can get a disc brake conversion kit fairly easily but the other modifications you are talking about require a whole lot more work. There are ways to remove everything and bolt on, with fabrication, a later Chevy front suspension and steering components. Kits are out there to use the Mustang II system but read the fine print to make sure they will work with your ‘61. Good luck.
If it ain't broke, don't fix it. My all original '61 Stepside rides beautifully,
