Well, I mentioned research as a way to strengthen his CV if he's already done a clinical rotation in radiology (personally, I am fairly certain my radiology research/connections/research letter is what got me my residency). However, since the OP has not done a clinical rads rotation yet, then I would start with that at the beginning of 4th year. I would argue that research in rads would help your CV more than a radiology away rotation, but that's just my opinion...unless you're set on one particular program, in which case an away can definitely be beneficial.