Reddit mentions of Gila RST T6 80mm Suspension Fork with 1" Threaded Steerer 160mm

I'm no expert on any of this so take my thoughts with a huge grain of sand:

1. Yes, the steer tubes of forks have different widths but you can probably find one that will fit your bike, which probably needs a 1" steer tube. Most aftermarket suspension forks are designed for threadless headsets, so you will either have to replace this and get a new bolt-on stem, or search around to try to find a sus fork that will accommodate your threaded headset. Here is an example of a sus fork that has 1" threaded steerer.
   
   
2. You can get a front rack that will work with a suspension fork. Old Man Mountain makes quite a few different models.
   
   
3. and 4. This goes back to 1. in that the first thing you need to consider is which forks are even available with the proper sized steer tubes for your bike. I think most if not all suspension forks are adjustable to a degree, but not all have a lock-out feature. A lock-out would be very nice IMO but not necessary.
   
   There is one major thing that needs to be addressed separately, and that is the fork offset/rake is going to be different with a suspension fork than what your bike was originally designed for, so the bike is going to handle differently. This might be either neutral or a bad thing depending on how attached you are to the way your bike feels.
   
   >Does such a thing exist? Does that even sound like a good idea?
   
   Yes!! Lots of people like touring with suspension forks. I think if you really want front suspension, it's probably a better idea to keep your bike as it is and buy a new one designed for suspension fork from the get-go.
   
   Frankly, your bike is something of a relic and IMO it would be a shame to mess with it. They really don't make bikes like those old Bridgestones anymore, which is a shame because they were superb machines.