The 2100S is the one you want for a 235. However, use caution if you're buying a reman, as some fords used that carb as well. The ford version, while externally the same (may say "Manufactured by Carter for Motorcraft" on the side), internally, they are different. The jetting is much higher (I've been told 150% larger than the GM version), and will make a 235 run very rich. I found this out the hard way, running 2 YFs on mine. The rear (ford carb) ran way rich. Swapped them, problem moved to the front. I ended up ditching the Carters for a pair of Holleys I rebuilt myself, problem solved.
