Small tools and Ajax seem to have listings in a plain back and can set you up with a back plate, an extra 1" won't amount to much. QMT has a direct mount D1-5 that is very good and reasonable if it is in stock.
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See if this makes sense... A few points. The 8" QMT is not available. Even though it has a reduced bore, I would happily buy one for $400... Chuck depth is very much a concern for work I intend to do through the spindle. In fact it's important enough I almost went 1340GT. However, the 1440GT won out for other reasons.
Looking at that TMX plain back chuck, the four mounting holes are 10mm and spaced at 3.252", wheras (on a backplate), the six D1-5 3/4" studs are spaced at 4.125" with additional potential interference from the set screws. So, to me, it appears one would need an extra thick backplate to work, to overcome this...
I have searched for pictures that show an actual TMX or Bison 8" (ind 4-jaw, forged) with D1-5, however, the pictures located show a 3-stud D1-4 mount! Looking at the TMX diagram, there's additional material on the back of the 8" to allow for the D1-5 studs. Or so it seems to me. I will try to upload pics later.
Since overall chuck depth is a concern, seems like a 2-piece jaw would be my best option to allow for closest tool access on shortest stock? I could use a two-piece jaw with the top jaw removed? LOL
I'm royally glad I am not in a hurry.
