About the fork swap.......
I have been keeping quiet on this project as it's not 100% completed yet. I had to work this out on my own as I made the same inquiries as you and came up mostly blank.
The following might be of value to you. might not. But you paid nothing for it so take it FWIW.
Do I have pictures? yes. Do I have the computer savy to post them here? Not a chance! I would gladly e-mail some if someone wanted/had the skills to make them show up here.
I love riding my old xt but modern dirty bikes are in my stable as well and being spoiled by modern suspension was the inspiration for upgrading the old girl.
I chose conventional right side up forks. Astetically(sp?) I feel they suit the bike better. The maintence periods/costs are less than associated with an upsidedown design. If you need the very latest tech forks on an xt, you are throwing a big $$$$ solution at a turd. A very likeable turd, but a turd none the less.
In the case of the DRZ conventional fork I used. It has a lengthy surface area on the upper fork leg to which you can clamp the tripple trees. If you look at a lot of fork swap projects on the internet they often appear like choppers in photos. Basically the forks on the modern bikes are all longer than what is required on the XT. This badly affects handling in many ways. Let's not get into this subject or possiable solutions here. The lengthly clamping surface mentioned above allows you to slide the forks up in the tripple trees returning the bike to it's proper ride height and hopefully wheel base. Vastly improving it's handling traits.
The problem with many upsidedown forks is
the upper tubes are tapered and the useable clamping surface is small, not allowing enough adjustment as required by the xt's shorter stature. This problem and many other are solvable but typically will cost serious dollars to fix.
Rather than adapt a bunch of stuff from different bikes I basically used all DRZ hardware. Brake, wheel, fork, tripple tree, stem. The forks I have, contain racetech one step up from stock springs which I had on hand. They perform well with the added weight of a heavier bike but I have not ridden the machine enough to know if they are required or not.
Many things need dooing but are basically simple jobs.
Welding new steering stops
New bearings Stock on bottom(nice tapered roller), modified(less than perfect but durable enough on top.)
Spacers to mount up headlight frame to new tripple tree
Figure out what you are going to do for ign switch mounting
front brake line routing
Steering lock (I have none)
Speedo solution(I have an aftermarket digital)
A couple of spacers here and there for the steering neck.
I also have Dr Big's up and foreward bar risers on my bike. Without this modification I would not be able to move the fork tubes up enough to return the bike to the correct (stock ride height) The tubes would bump into the bottom of the handlebars otherwise. If you go to thumpertalk and search DR Big risers you will get a million hits on them. If riding a DRZ with this modification you will never consider going back to stock. They are awesome. If you have the skills to make your own. Do it.
The results from this project have been teriffic. Vastly improved suspension action. Stiffer front under braking loads. And improved braking force. I have put in about 750 Km of off pavement riding and have experienced no evil suspension traits to date. There is no where to hide bad susp. traits in off pavement riding, they will show their ugly head! But not enough testing has been done yet for me to give it the full thumbs up.
The problem created is the 25yr old rear end on the xt seems that much worse. Please spill if you have good solutions to this problem.
I'm no expert mechanic or suspension tech but pulled off this mod sucessfully. So can you.
A final note of caution:
I have learned that suspension geometry is both an art and a science. Changing stuff, wheel base, ride height, trail, rake, fork offset, axel location, can go horribly wrong and will be very expensive to make right.
If straying far from what the OEM's have figured out for the machine. You are proabably going the wrong way. They have done the math!
Each bike and fork combo must be carefully considered to end up with a workable solution.
The experts will laugh but basically I eyeballed most of the variables discussed above (in side by side comparisons of parts)and applied my very crude understanding of suspension. To this I threw a bunch of cheap parts sourced from fleabay. I rolled the dice on this project and think I won.
An underlying principal was, always be able return the bike to stock if I messed up. No permanent changes were made before I could road test the machine. If it didn't work out I would just flog the parts for little to no loss.
The bike is a 1986 xt 600 NAm. model, 43F for the euros (note: early xt=longer travel susp. than later bikes). The front end parts came from a 2003 Suzuki DRZ 400s.