Either CGR, IGES, or STEP will work. Since CGR is not an option in v4, then IGES or STEP will have to do. I have someone starting to utilize the translation utility in CATIA version 4 to do the conversion. I'm waiting for results from him. In the mean time, I'm trying to find another solution. I have read the CATIA models into the software FEMAP. When I wrote out a STEP model, the conversion was not correct. When I try to write a IGES model from FEMAP, no output file appears.
Now, I've downloaded the CATIA v4 to IGES software from CADLINK, and am about to test it.