The head and pistons just bolt straight in/on so its just an engine rebuild.
The only thing you would need to sort for twin carbs is the inlet manifolds, throttle linkage and electric fuel pump.
The cost I didnt really keep track of but I got the 2002/518i parts for around £100, carbs for £200, inlet manifolds for £70ish.
The 292 cam was probably the most expensive part I bought.
Check out
www.Jaymic.co.uk they are brilliant for M10 parts.