Why is my truck so squirrely?

[Number21]

I'm just getting my truck back on the road after sitting about a year. I've been driving a 2001 dodge, so that's what I'm used to. Getting back into my '73 with 33" tires feels like driving a school bus.

Problem I'm having is it's very hard to keep a straight line driving down the highway. It does not seem to favor one direction or the other, I just look like a drunk weaving back and fourth. I know this thing isn't a caddy but something has to change. Its like driving a boat.

I don't remember it being this bad before I stopped driving it, though it wasn't perfect then either. What do you guys think is causing this? Is it my big ass 33" tires? Lack of sway bars? Other suspension problems? Steering issues?

I don't expect a perfect ride but I'd like to stay on the pavement...