David Hodson is absolutely correct. 4th Generation iPods can use drives from 5GB up to 80GB that have the pin style connector, not the ZIF. 4th Gen iPods can also use any Toshiba drive that ends in 004 or 006, such as MK4004GAH, MK2006GAL, MK2006GALC, MK3006GAL, MK4006GAL, etc. The HDD that you have chosen is a ZIF connector and will not work. Attached a couple of images for you to see what I am referring to, hope this helps.
This is the 4th gen HDD. Check the connector. I believe it is a DDKLtd, MCD-D50SA-3 Here is the HDD from an iPod Classic, it clearly shows the ZIF connector....sorry does not work on the 4th gen. Now if you really want to do something different and advantageous, change your 4th gen HDD to a Flash drive.....works great an less risk of failure. Anyhow, I hope this answers your question. Good Luck.