An aftermarket front drum is a total waste of money in a 904...Unless your turning higher rpms then pro stock, they are not prone to the same catastrophic failures as 727's.
It's not a waste if you want to add extra clutches the right way instead of sticking skinny ones in that heat up . He said it's a 600+hp race car , by your logic he should just run a stock trans then eh ? My motto is build it right and never have to worry about it if you want to cheap out and risk having to do it twice have at it , my car has been cross country 2 and a half times with no issues in the trans and the people I let drive it will tell you straight up they beat the heck out of it with no signs of problem .