The inspection cover does help with structural stability and shall be bolted with the correct metric bolts.
As far as the strut braces that go from the inspection cover to the motor mount frame brackets they are not bolted on the CUCV for whatever reasoning, lighter T case 208 perhaps but why they are not on the 205 is anyone's guess.
However they are bolted onto every civilian K Model 4 wheel drive truck 81-87 from GM, and up to 1991 on models that retain the "square body" shape, K5 and K30 Crewcab, and Suburbans. The civilian transfer case to the engine bellhousing has one also, that are prone to shearing the bolt from the T case to transmission, at the transmission from stress also. And do not replace bolt with a higher grade bolt as instead of the bolt shearing at the trans, block will crack at bolt hole or break the block casting.
I had one 454 block that was the recipient of such a "repair", but that was with a 205 T case. The trans was welded and saved. And I have another CUCV 400 that broke in half at the T- case adapter that had a 208 bolted to it.
The 400 is a very good transmission and every one that I have seen in cars have not had the problems associated with K model trucks. And I have K30 400's in 454+ci Monte Carlo's with the bolt on pan and shield for the xtra rigidity.
Believe it or not, your choice.