I have a second hand crank for an E6 available which is only just run in at 16,500 miles. It comes from my old engine which suffered block damage due to con-rod failure. The crank is perfectly OK and was not damaged.
It will also come with matched main bearing shells (see 9 and amp; 11) and thrust washers (12) for the included beam carrier (8) which may or may not be useful to you depending on what you want to do.
I am not 100% sure if the E4 and E6 cranks are compatiable but the E6 and E5 cranks are definitely interchangeable (same part number).
Check with Ralliart and get back to me if you are interested.