Transfer box replacement - used or recon?

Advice guys I think the viscous coupling is on the way out on my p38 which has done 148k I have had it since 75k new engine at 125k so am thinking if the coupling needs replacing is it worth replacing the transfer box and if so a second hand unit or is it better to get a recon unit - I was looking at Ashcroft any suggestions welcome

get a second hand scrapper and trade it for a recon....

good point well presented ta