Been down this road.
As you can see, the original v6 swap required that the front prop shaft be lengthened and the bellhousing cross member cut away to clear. Looks like a new transmission cross member was fabricated and welded in. In addition, the drum brake was simply deleted as it was apparently too much to figure out a solution.
This new config will be a huge loss of the lovely granny first that makes the SM465 is so desirable. 'Twere me I'd get the SM465 to Series transfer case adapter, and perhaps even do the RRC/Disco 1 diffs. The V6 can push all that easy. Way less re engineering.
They have no choice but to install an X-Brake. The original mech linkage would never work anyway.
1966 109 5 door wagon 300Tdi "spermaceti fueled"
1994 RRC LeWiB "ruining the air behind me"
1968 2A 88
All my troubles are Rover