I concur, Ford AND GM should have stayed clear of the V8 diesel design. However, Navistar already had a small V8 engine that Ford could utilize and it was kept as a V8 for all iterations. $7K is a hefty premium to pay for an engine that costs more in fuel (by the gallon).
V10 parts are out there. You just have to search. As the V10 is considered the 'work horse' gas engine (as compared to the 4.6/5.4L mills); you might want to check out performance RV websites. Bankspower.com is a good start, and if anything, they can forward you other sites to check out.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!