Hello, I hope the following is of assistance.
Given the very fine manufacturing tolerances on this engine Ford didn't produce any internal components for the cylinder block assembly, this means the crank, bearings, pistons and block are not available as Ford part.
There are a couple of options but unfortunately neither will be easy or cheap. A second hand engine will be the cheapest but these seem quite difficult to source mainly due to the fact there are no internal parts available.
A short motor will still be available from Ford which is a new cylinder block, crank and pistons but this will be quite expensive and in all honesty more than the value of the car.
I would confirm it is definitely the small end bearings as this engine does suffer with inlet manifold problems where the swirl flaps come loose, this does make quite a loud rattle when this happens.
I hope this helps you but if I can advise further let me know and I'll reply as soon as I'm able to.
It is defiantly not the flaps as these have been removed...could it possibly be the valve buckets? The cylinder head was replaced recently
if you suspect the valve buckets then I would check the valve clearances as nobody really adjusts these on this engine, many people think they are hydraulically adjusted but the aren't.
There are no shims either the buckets are different thicknesses, they are marked with the thickness but only the decimal place part for example .650 is 3.650. If the clearances do need adjustment then the camshafts need to be removed.
Let me know if I can assist further.