1965 dart gt spring question

Manageability is an interesting question. You may like having a car that can "spin out" on a damp corner and face opposing traffic in unpredictable ways. It does make for an interesting driving experience.

Or you could listen to others that have already tried this, and choose smaller rims and tires that actually fit within the wheel wells.

On my '65 Dart I run 15x7 inch rims with a 3.5" back spacing. This allows me to use a P235 60 tire. This combo fits without any heroics with plenty of space between the springs and fender lips. My rear suspension setup is 5 leaf springs with a 8.25" axle. With stock shackles and front hangers located in the stock locations.

But before going out and spending money on wheels and tires, fix your current suspension problems.