Will this 904 trans work in 65' Barracuda?

If you want to use the pushbutton shifters you will need the 904 specifically for the cable shifters and the correct year valve body. If you're wanting to use an aftermarket floor shifter most any 904 will work. The difference you have been told about for mating a 904 to a 360 is that the pre 68 torque converters have a smaller snout on them than the later models. You can get around this with a spacer from Torqueflite Patty or by swapping out the front three main components in the PB tranny to a 68 and later parts to get the more modern input shaft so you can use a later style torque converter. 360s use an external balance converter and the pushbutton trannys were for internal balanced engines which can be covered with an adapter flexplate by B&M, by welding ablancing weights to a converter or by usig a converter for external balance.