24 Valve Head

Hi guys, does anyone know if the 24v head off a 2.5 will fit straight onto a 12v 2.5? If it does, what do u have to change with regards to the timing chain on the 12v engine? is it just the crank pulley or do u have to change the crankshaft as well to accomodate the timing belt? Was considering the swap on an E30 325i sport. Anything else i should know while on the topic?

I've heard of people attempting this swap at enormous expense. You are better off just swapping in a whole M50 motor, it is well documented and much cheaper in the end.