@ Chris Tindal: Same with mine. Both of the horncasts I had were stamped Innocenti but one is narrower. So the original one needs to be repaired and painted.
I had a very similar issue wth a horn cover, too narrow to fit the holes in the legshields by about 6mm and too short by about 4mm. Both have Innocenti and the part number cast into them but only the genuine Italian one - the one that fits- has an additional casting mark 'P1477' and the FP mark.
I can only surmise that SIL changed the casting for their later rounder shaped legshield.
"Our dilemma is that we hate change and love it at the same time; what we really want is for things to remain the same but get better."
Checked the horn casts - both have P1477 and FP mark. Very strange. Will measure the horncast of my DL150 from 69. Maybe a difference from early to late DLs
Villmark, I think its just the poorer quality of Indian horncasts. They look like the same casting but haven't been opened out to match the legshield holes, so are therefore misshaped. That's my view anyway, and I abandoned a new one and got my original drilled and tapped by a local engineer, glad I did now. I guess with some heat and patience they could be made to fit. Rosscla I actually disagree with the later rounder legshield thing, I think both profiles types could be found with Italian machines.
I only say that because back in the early 80's I had two GP's, both original factory spec, a 200, then a 150. The 200 had the curved legshields and the 150 had the square type. Before I bought the 150 I actually thought it was an SX with GP headset and panels etc. because I was used to the curvy ones on the 200.