Options for 73 /6 904 flex plate

I have a 73 motor and trans and I bought a 904 BM six bolt zero balance flex plate thinking it would bolt up to my crank flange NO LUCK


My question is what are my options for flex plates? This is for my turbo build and I hoping to make around 450 to 500 hp at the crank with a 3200 stall and a rev manual vavle body 904 also I'm running 2.94 suregrip 8.75 rear


I'll have to get some measurements of the torque converter distance between the bolt mounts for the flex plate in the morning


Thanks Aaron