If you are trying to get a substitute for a certain ferrite, look at the following:
Shape availability
For the material mix, the saturation flux and the losses per volume unit at your operating frequency (usually at a temperature of 80~100°C). Compare these against the original.
The Al value is not really that important: for flybacks it is dictated by the airgap, so it depends very little on the actual ferrite material. For forward-derived topologies, it is generally sufficiently high. Slight variations will cause some change in the magnetizing current, but generally nothing serious. I never worry about it.