Well we now know he still has that stock or rejected heads so can still recommend not going near Les with a bargepole.
If the thread is the only issue then I think it can be used as is or new threads installed, the threads wearing out is a common issue so the fix is available. The factory did have a run of porous heads giving issues with oil leaks from odd places on the head. Their cure was to have the heads injected with a resin to fill the voids and stop the leaks.
The process was similar to this one
During the casting process, small voids or holes can form in materials when changing from a liquid form to a solid state, this is called micro-porosity. Despite these small holes being hard to see, they have the ability to cause detrimental effects to the quality of the finished product...
www.impregnation.co.uk