It's upto you if you get one BUT it aint gonna hurt is it.I noticed this as well so i bought one.Got mine form Forge Motorsport but i think A1 rallysport sell them as well.And Yes you do need to chop off that offending chunk off block.And you can cut it with a good quality hacksaw as if you use a disc cutter your spraying iron fillings everywhere which will rust and cos problemms later on.
HTH