The fruils for the 251 are number ATL-61 and I can say they are a lot more complicated than the normal Friuls. Once you build the normal run of tracks you have to add in the track pads. I have two sets and to be honest I'm not sure I'll get to use them for a while as I don't trust the glue to hold the track pads forever.
On top of that I'd agree with the other guys on here get the AFV or Dragon kits of the 251 they are better kits, use the Tamiya and a learning one and get your skill up on filling gaps etc, I did that with a Revell kit of the 251 and it was useful even if the kit isn't that good
Phil