I did my own TnT a couple years ago. Between everything, I think it was $600-ish. Kubota, and the local independant near me wanted $900+. I know why; it is not cheap for the parts, much less the labor to build it.
To do again, I would use welded cylinders. Don't get the Prince 3-spool valve from Northern. Although it is probably a great valve, when I got it and place it on the fender, my Kubota fell on it's side. Imagine the intro from "The Flinstones" with the rack o ribs /forums/images/graemlins/grin.gif Ok, not really, but close. It was HUGE. I sent it back, and got a small 2-spool "Metro" from the local repair guy.
If you are going to the effort of T, go for the extra valve spool so you can add the other "T". I find I use the tilt more than the top link.