Ever drive a late 70s F150? Drive nice, don't they?
That is basically the same design solid axle swap that most guys end up sticking under their Explorers or Rangers.
What's the problem?
Note that I'm actually a fan of the TTB for certain things. They ride better in certain types of off-road work, they have some great capability for desert work, and they do well, if properly built for the off-road stuff, but they are ultimately limited for tire size, and really hard-core wheeling.
If you are only wanting to stick to 33 tires, I'd just stick with the TTB. If your truck is newer than the TTB, and has the full independent front suspension, then yes, it is better to SAS, for there is basically no way to get much in the way of flex out of that suspension. Not to say that there are no trucks doing well with the IFS, though... Gerald's truck is great and very capable, but he also has a lot of repairs. I've been with him a couple times when he has had to replace the front axles...
Cost issues TOTALLY depend on what YOU can do for yourself -- your patience in searching out a replacement axle setup, etc. I'm in progress of swapping in a 44/60 combo in my Ranger, and the entire job is going to cost me less than $1000 (mostly gears and lockers). Of course, I'm building my own links, picked up the axles, tires, wheels, and some other parts, for a trades, etc. Others have said that it will cost up to $2500 or more to hang an SAS front axle if they have a shop do the conversion work.
Is it worth it? You know what you want to do with the truck... They get real capable with the right setup...
