My first mishi had that problem. I spent more than half an hour using a file to remove excess aluminum so that the shroud fit properly. While you're doing this, it's critical to ensure even clearance around the fan blade perimeter with the shroud, otherwise you're asking for catastrophic failure.
My first mishi lasted 3 years before it sprung the well-known pin hole leaks. Not catastrophic, but a failure nonetheless. My warranty replacement mishi did not have the fan shroud mounting issues but did have another fitment issue: the overflow nipple was soldered on too close to the upper hose nipple. Consequently, I could not put the hoses on because of clearance issues. I wound up using a propane torch to heat it up and bend the overflow nozzle so i could get the friggen hoses on.
These rads are never a direct bolt on!