So what are you editing in? 1080?
Based on your info it sounds like you shot with a regular lens so the only way to get 2.35 is to letterbox it. You can have compressor crop off the letterbox for delivery, but you’ll need to do some math to figure out the dimensions of the resulting file.
for instance a 1920×1080 movie with 2.35 letterbox would have 1920×817 pixel of actual image.