There are the nipple type clutch centres with or without the spindle plus - as you suggest - the GP type that never had a spindle.
Your choice should depend upon which crankcase cover you have.
Just for information, the ‘strong’ Pacemaker gearbox was only reputed to be available without the centre bored to suit the spindle, yet I found one that does have the hole. So, you could reason that the ‘weak’ gearbox might have been available without the hole

If you haven’t already checked by measuring, it may be worth doing so
