No recipe but I used about 6 1/2 lbs grapefruit per gallon. around 4 cups of sugar per gallon to get to 1.090 Used yeast energizer and EC1118. Also added wine tannin the last few times we made it. Removed as much of that white stuff from fruit as I could and put pulp into cheesecloth.
It has been many years and the notes I made back then were just scribbles on post it notes.
Are you planning on fresh grapefruit? I have a very nice concentrate or juice recipe that uses white grape juice as well. Very good, simple recipe with frozen concentrate or commercial juice. You might be able to adapt for fresh grapefruit juice.