Thanks for all the advice! I had not received notifications of replies, so I guess I need to check my forum settings.
I went with a non-suspension Tractor Supply seat. It is called "Black Talon". I think it was around $130.
I cut the two brackets off the old Kubota seat. They are sloppily welded on the ends so it was easy to grind down the weld then split it with a cold chisel.
In addition to the adjustment holes on the sides of the brackets for seat position, there is also one hole on the bottom. It is just a plain hole, no bolt goes through it but it does save you from having to drill a hole, since you can run the hold-down bolt for each bracket through it.
The center-to-center the old Kubota seat of these holes is 17-1/2", and the two pairs of hole spacings on the Talon seat are exactly the same. That means that when the brackets are attached to the seat, they fit the pivot member perfectly, and that the bracket can be mounted in two different areas on the seat pan.
The only problem with using that one hole is that the bolt head will prevent the use of the middle of the three pivot pin adjustment holes.
I tried a few positions, but decided to go middle-of-the-road. I used the most forward position of the seat pan holes, coupled with the rearmost adjustment position with the pin pivots. Here, I can look straight down and see the entire shifter boot, and the seat is not so far forward that I have to do the high hurdle move to get off the tractor, nor am I so far back that it have to lean a lot to steer.
So, I was thankful the seat pan bolt holes, two pairs of them, were exactly 17-1/2" on center, identical to the Kubota.
If I had used the next pair of seat pan bolt holes, I could have a seat which sits way back, or very close to the shifter. Like I said, I could not use the middle pivots because the seat pan bolt head does not clear the rubber pivot bushings holders. You could probably get the middle adjustment if you ground down half the thickness of the bolt head, but I found I could get the same position by using the frontmost set of bolt holes on the pan with the rearmost pin position on the adjustment bracket.
However, the biggest problem was that the 3 pt hitch lever hit the side of the seat where the trim is.
To fix this, I bent the lever toward the fender more, as much as I could manage without removing the fender, and I bent the seat trim and the metal flange supporting it (thus making it non-returnable), with a deadblow hammer.
The combination gives enough clearance.
One alternative would have been to put another hole in each seat bracket slightly offset, to make the seat slightly offset. That might give you another 1/4 inch.
As far as the seat itself, it feels good and feels well-made. I do think I would prefer the same design but with half the height in the back. The back tilts backwards, and I never would drive it that relaxed. You don't lock into the seat--no bolsters, so don't nod-off while you are driving. If you do mowing where you duck to miss branches, be aware that you may clear but the seat might not.
The seat is made in China, but the pan holes are 5/16" SAE. You will need two bolts about 1/2" long, with a plain washer, and definitely locktite on the threads or a lockwasher.
The seat pivots forward just like the original Kubota seat- that keeps the dew off it and the hot sun.
I don't see any mounting bracket of the back of the back for a safety triangle. The original Kubota seat had that and one or two other brackets I never figured out the purpose of.
Pics later....
