904 6 bolt crank flexplate internal balance

Well i got a reply from bm and they state they don't have a flexplate for our 340 internal balance 6 bolt crank 904,I find this odd.I see PRW 1844010 says it fits both 904 and 727 and is sfi any thoughts on that unit,just have always used a bm with our big blocks never thought this was going to be an issue,figured it would be pretty standard stuff