a lot of the 24V converted sierra's have this problem with no ill effects
it's the springs that rattle and as soon as you put just the tiest bit of pressure on the clutch pedle it goes away

if it's anything like the spigot bearing going you'd soon know about it

and if it's the main input shaft bearing you'll soon know about that too as they tend to oval the input shaft oil seal which dumps loads of oil into the bellhousing