My '82 K2500 had those strut bars hanging under the truck when I bought it..they were bolted on at the motor mount pad bracket--but the TH400 someone put in it was not a K case that had the provision for the aluminum dust cover for the strut bars to bolt onto--they were just zip tied up out of the way..
I was told the TH400 was from a big block Chevelle that was rebuilt with a shift kit and had low miles,and the owner decided to swap in a Muncie 4 speed setup in the car instead,so the former owner of the truck snagged it for the truck..it did have the 6 bolt low stall speed diesel converter though,I'm guessing it was swapped in from the original truck TH400..
I have plowed some very deep snows with this pickup over the 15 years I've owned it and haven't had the bell housing crack or any other issues yet--I haven't taken it off roading or got it airborne,but I have rammed some hard packed snowbanks dozens of times and haven't busted it yet..
I say the strut bars are nice to have,but probably not a must for on road use..if you had a NP203 or NP205 hanging off the back of it then yeah,I'd want them for sure--but a NP208 isn't that heavy and it does have a long truss bar that bolts to one bell housing bolt to help keep it from stressing the tailshaft housing on the transmission..