Attack on stream cipher that XOR's the output of two LFSRs
There is another method named algebraic attack.


Name each of the keys initial keys by $l_{1i}$ and $l_{2i}$.
Since the LFSRs are linear and the combining function, x-or, is also linear compute algebraic equations
Solve them. They construct a linear system of solutions.


Since only 38 bits are keys, you will only need 38-bit output if the if the equations are linearly independent. 

if you use the Gaussian elimination method it will have $40^3$ operations.