904 to 360?
external B&M flex plate and i think thats all
And why???
DB15 is close, heres why.
The 360 is an extrnal balance engine. To use a 360 with a 904 will require the use of it's stock torque converter and damper. Or a aftermarket torque converter and damper that works on a 360 as like the stock parts do. AKA balanced the same way. Not internally balanaced
IF, the current 904 trans is in use with a 273/318/340 internally balanced engine, as these are balanced this way stock from the factory, there torque converter and balancer are made for use with them, not a 360.
The B&M flex plate is for use with a 360 and a internal balnced converter. This is a cheap and easy way to install the 360 and go.
IF the 360 has the torque converter with it, just use it and bolt it in.