Cannot tell which series of Ferd this is. If it had the 6.4, that engine is a time-bomb and works great until it doesn't. Some of the 6.7's suffer from the CP4 grenade and owners simply do not want to drop the $$$$ to prevent $$$$$ in repairs when it blows.
More common path is one of the inline 6 banger Cummings instead of a V8. Or, look for an older HEUI model as even the "dreaded" 6.0 was reliable once bulletproofed. Just don't ask for crazy numbers like 700ft/lb out of a HEUI and it should do fine with supporting mods. But, social media is full of folks who simply want to slap things into a truck and then complain when it kills the powertrain.