I would say between a 3406 and n14 it boils down to personal preference over all. I've seen both do a million plus miles with nothing but simple maintainence. The 3406 n14 and 12.7 series 60 pre egr were the best engines ever made hands down. The c15 isx and dd 15 would probably be just as good if they weren't so over loaded with emissions equipment. Certainaly enjoyed this thread 10 thumbs.
Oddly enough the allis chalmers big al was the buda 844 with newer injection and turbo tech. And the paccar engine is of DAF design. DAF being a DUTCH truck manufacturer owned by paccar.The maxforce13 was a joint design between navistar and MAN a austrian truck builder. The maxforce 15 found in moebius kits is a c15 cat with navistar injection and emissions. By the way cat had 2 engines they tried in trucks in the 40s with no success but reentered the truck market in 1962 with the 235 hp 1673 installed by a cat dealer in new ih emeryvilles for denver chicago trucking..Popularity wise Cummins held the crown till the late 80s when the series 60 detroit came out. As far as million mile untouched engines go I would give that to the n14 cummins based on the fact there were far more n14s than 3406s built both were great engines and better than anything made today.
Actually none of them were ever hot sellers. They go together well and are decent kits but are very simplified by 1/24,1/25th scale standards as they were aimed at the youth market. But there is tons of room for super detailing.
Actually the allison v 12 is physicaly much larger than a detroit v 12. The detroit v 12 is a whisker under 14 litres the same width and height as an 8v71 and a little longer than a 6 71. As far as the allison goes Tyrone Malone put one mid engine a coe freightliner many years ago as a wheelstander. Last I knew it belongs to Gary Riese as well as the Super boss and other Malone stuff . Certainly would be a neat project.
There have been several small companies that have made big rig conversions for pu's of varying degrees. The Revell kit you mention dates back to the 70's as the sneaky pete kit. I've seen one's close the kit but not exact.