The Astro 4.3 was available with three pedals 1985-1989. It had possibly the strongest NWC T5 and the only 11 inch clutch with a 1 inch 14 spline hub. This I know because it is very relevant to my 1980 Buick conversion. Also, the T5 currently in my car is from a 1986 Astro 4.3.
Of course it was certainly quite rare for anyone to actually order one that way, I assume, as they are super-rare now.
It was a miracle when I stumbled on one at the Pick 'n' Pull. It was under 40°F, raining, and an hour or two until closing time. My aging, non-mechanically-inclined dad was with me. We ripped that bitch out like cavemen. Unfortunately there wasn't time to get the clutch disc, but I don't think the 11" disc will fit anyway; my flywheel/clutch cover assy/pressure plate is for 10.4" (but there is no 10.4" OEM application, only an expensive custom racing part, so I use a 9" or 9.4" from more common applications).
Dad thought I was nuts buying a transmission for a failure that hadn't happened yet, but a year or two later I needed it and finding any appropriate T5, let alone that extra-strength one, would have required time and money that I wouldn't have had...it sure was cheaper getting it when the getting was good, and it was great having it in-stock when I needed it!