Auto makers say the Deisels and manuals no longer sell well and they need to have a certain volume of sales to make it a viable option to carry. Diesel isn't that cheap anymore, and you have to do the Urea and many filter thing with them now days, that costs more. Myself don't mind a BIG truck with a 4spd as in old days, but really not a fan of shifting constantly with 5 or more speeds like most vehicles seem to have in them now days. GM and X-ler had their trans plant for the big 5spd together, cause was only way to have the trans be cost effective for both company's. NOW, orders were low and they closed that pland and both quit offering one. Even the Fords have foreign made manuals in some of their offers last few years, not sure they have now.
ON that Dura-max Six, not sure they would put it in the smaller truck?? It is Still a BIG engine, have seen them in past. I work in big truck plant and we had some setting around about 4 yrs ago. Then the big crash and bancrupt and was put back on shelf. Talking now about bringing it back again, but nothing happening at our plant about it. Idea was to have a Diesel in a half-ton and not the 3/4 or bigger it takes now for bigger engine.