Note there is a posted US 50 Truck in ancient GMSV (latest available) in West Union, running both directions on former US 50 leaving WV 18.
No idea if it is still there. It is clearly for trucks going from WV 18 to US 50 east ore west. US 50 itself has no need for a truck route.
I visited this yesterday. US 50 Truck is still posted from WV 18 SB. There are 3 truck US 50 East postings and 1 Truck US 50 west posting. All 4 are on WV 18 SB. I drove the entirety of the roads both directions and there were no further US 50 truck postings.
Oddly, there is no WV 18 Truck. WV 18 has two 90 degree turns close to one another with an old bridge in between, plus an awkward sharp S at a railroad underpass between the US 50 truck postings and US 50. Either would be difficult for a large truck. They must be pretty confident there are no thru-semis on WV 18...any would only be getting on US 50. I saw a bunch of large trucks on WV 18, though no full semis.
Incidentally, WV 74 has several right angle turns within Ellensboro and trucks over 50 ft are just prohibited from going north of old US 50 on WV 74. There is no truck WV 74 either. There are signs at the WV 18-74 jct for trucks >50 ft not to use WV 74 which forces them down WV 18 to get to US 50.