A833 O/D Cover/Access-plate installation

The Struts HAVE to match the brass!
The pre71 transmissions had the solid metal narrow struts with matching narrow-slot brass. The 71 and later had the lightweight hollow tin struts and matching wide-slot brass.
Your cover is a 71 Up Scissor style.
To install the cover;
The reverse lever has to be installed into the case before the cluster goes in.
To install that cover lube the O-rings with Silicon grease, then install both of them into the cover. Put the trans in neutral. Install the 3-4 fork into the scissor with both blades on the pin. Install the 1-2 fork into the slider groove of the 1-2 synchronizer. Install the gasket onto the cover with a few dabs of grease to hold it.
Now the tricky part;
You have to drop the loaded cover into position while simultaneously indexing the 1-2 fork into the scissor. It's not that hard, but just tricky, and I recommend a couple of dry-runs without the gasket, to get the hang of it.
Sometimes I have to put both the trans and cover into Third gear. However you do it, ONE fork has to be already engaged with BOTH scissors.
After the cover is in position, go find the two bolts with long shoulders and install them in the deep holes that run at about the horizontal center-line of the cover. Run them down finger tight, then push the cover hard up and tighten them. Now try to shift the trans into reverse.
If it goes easy, you are in business, loosen the bolts and install the rest, without cutting the gasket. The three bolts near the reverse lever have no shoulders,but do have split washers; the rest are short shoulders, and I don't remember any washers on those. Then, once again, push the cover hard up while tightening those first two bolts, check reverse and if it still goes in then you can tighten them all.
Now, in the event that reverse binds and will not in-shift, or does so only with great difficulty, then you may have the wrong reverse lever installed. This only rarely happens and if the lever you installed is the same one that came out of it, then no sweat it should be fine.
But if not, then those levers come in two flavors, a long and a short and are coded..... but I forget which is which.