If still looking for a 200-4R dipstick, here's one. A bit pricey but brand new:
TH-350 TH350 (THM-350 THM350). 1985-1986 Pontiac Bonneville 6 Cyl 3.8L, 6 Cyl 4.3L, 8 Cyl 5.0L 2 DOOR, 4 DOOR, BROUGHAM 2 DOOR, LE 2 DOOR. 1992 GMC Typhoon 6 Cyl 4.3L 2 DOOR, 4 DOOR. 1991 GMC Syclone 6 Cyl 4.3L PICKUP.
www.ebay.com
If you need the fill tube, it's 25508003.
Find many great new & used options and get the best deals for New OEM 86-87 Buick Regal Tube Assembly, Transmission Fluid Filler 25508003 at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Diesel or gas uses the same junk on G-body 200-4R as far as tube and stick. I think they used the same tube from 83-89, changing in 1990 on the
B body.