I cut it form each of the sides, about a couple of inches, in a straight vertical line. Basically was going to narrow the shroud to fit on the 7M auto radiator. The Aristo radiator was too wide for the MKIII frame. I was going to trim these pieces of the shroud and then join back tohether and use some sealant on the seam, so that it would only ally the air to be move where the fan makes it.
But I ended up putting a USDM 2J waterpump on, so I didn't need to modify further.