Gearbox and axle ratio advice please

[1000wannabe]

Hi Everyone,
I'm in the planning stages of my next restoration, an early Series 2 LCV.
When I got the van, it was without the original engine and gearbox but still has the original diff ratio.
Can anyone here with lived experience driving cars with earlier drive lines provide some input please?

I will be fitting a 948 engine (because I have 2 spare) and an 803 is out of the question because of where I live and I remember how unsuitable they generally were for use in Australia.

My dilemma....

I can either fit a series 2 gearbox that I have (in good condition) or a series 2 box with 948 ratios fitted that I also have. (So effectively a Minor 1000 box but with the earlier shifter.)
I also have a 4.55 Minor 1000 diff centre I can swap in..

Because the car is early, it has the speedometer mounted on the right, so I can't swap it with another tpm speedometer like you can with the centre mounted units.
I want the speedometer to be somewhere accurate. I realise there are issues here, hence the questions.

I live in a hilly area. The roads are a mix of either winding and climbing (sometimes steep) back roads, or, the roads they join which are high speed (100km zone) roads with limited overtaking opportunities for others and /or, high speed areas with LONG steep climbs (with some passing spots).. when I say long and steep, they have big trucks and milk tankers literally at almost walking pace as they climb the hills.

What combination of gearbox and diff would you guys recommend?
(And save some people typing, engine swaps are out and rib case gearboxes for Minors are basically non existent here)