Aftermarket Chassis, Which one for best ride quality

[theastronaut]

Ask how much bump and droop travel those chassis have at the wheel, you'd be surprised at how little some companies build into their suspension design. The less travel they offer the stiffer it has to be to keep it off the bump stops.

"Coilovers" aren't anything special if they're not made for the application and usually offer less travel than a separate spring and shock. You can tune spring rates and shock damping without going to coilovers.

The original 63 up front suspension has pretty good geometry already, you can tweak it with taller upper ball joints to add more camber gain, a rack and pinion kit to tighten up the steering response/feel, and modern alignment specs and have a really nice riding and driving truck. The stock suspension will offer a lot more travel than most of the aftermarket frames will, even when lowered 4-5". Try a set of adjustable shocks on the stock frame first, you might be surprised by how well the stock suspension works with some tweaks.