This sounds awfully high to me. I wasn't able to find the current breakdown but I did find the Marine casualty statistics from Viet Nam:
Protestant: 61%
Roman Catholic: 33%
This country has always had between 17% and 23% Catholics,the fact that 33% lost their lives in Nam supports either that Catholics go into the military in higher numbers than non-Catholics or are more apt to die.
I don't know about the 60% number either.