I don't know the answer, but I wouldn't do it. I'm not sure on the late run GMT 400s, but the GM heritage literature for the early models list the crew cabs as having a higher "section modulus." If else is the same as far as depth of frames is the same, then the crew cabs are thicker frames. Also, I recall the document stating the C/K3500s was thicker than C/K2500s. I posted the number on a thread recently. Perhaps someone knows what the actual thickness is for the later models.
I've got a '00 CCLB K3500 if someone is interested I can measure the frame thickness with a dial indicator and compare to someone else's RC/EC.
My BIL and I recently looked at a K2500 CCSB for sale locally. Guy was asking $3700. It had a few issues, but not too bad. My BIL decided to pass on it, unfortunately.
