I believe this is the link you're refering to.
http://www.vortec4200.com/forum1/viewtopic.php?f=7&t=782Lengthwise the 4200 is slightly shorter than the 235. The only problem is that is has a fan clutch and the 235 doesn't, thus making is longer.
If you go with a electric fan, problem solved.
If you want some specific dimensions, I have a 4200 on the engine stand right now. I would be more than willing to help.
Chris