Don't talk to me about axle swaps, I'm not gonna give you the advice you want to hear .

The solid axle swap is highly overrated. The IFS on these trucks is sturdy, and will go almost anywhere you feel like you need to. There's a culture that says you have to have a solid axle or you're not wheeling, but I call bullpucky. With the time and money you'll spend on just the solid axle conversion, you could afford plate bumpers, skid plates, rock sliders, and a selectable rear locker, and have a WAY more capable truck, with a better ride and better mpg to boot. There's a reason Toyota went to IFS - for 99% of the wheelers out there, it truly is a superior all-round system. And unless you're taking lines like this, you're not one of the 1% that actually needs the strength and articulation of a solid axle. It's a nice upgrade, it can be strengthened where the IFS can't and is easier/cheaper to get higher lifts. But it's far from necessary in order to take your truck places that'll have your butthole grabbing seat cloth, and I think in your case it'd be overkill. Wait until you're breaking the IFS you've got, then worry about if it's time for an axle conversion.

To answer your question, when you install the straight axle you'll be removing the torsion bar suspension and installing leaf springs (or coils, if you're linking it) - the suspension is how you lift the truck, so you only want to do that once.