Aluminum CX frame with steel fork.

This was the combination I used on CX bikes from around 2002-2004. After that nearly every CX bike had a carbon fork. I raced on one like this back in the day and only sold it after I got injured and had to sit out a season. 

The steel fork is heavier but it is a lot less money and I can build it with any rake I want. There's not much variety in carbon CX fork geometry so this is a bit of an advantage for certain size bikes.

The owner is not a total Luddite, though- it will have modern flat mount disc brakes front and rear.