UK metric system:
1 furlong = 10 chains
1 acre = 1 furlong x 1 chain
I remember when we finally got rid of the rod, pole and perch - which were 1/4 of a chain! So a furlong was 40 chains or 220 yards.
At RAFC Cranwell, our USAF War Studies instructor gave us the speed of the SR-71 in British Units...furlongs per fortnight....
In the MKS system, fuel consumption should technically be cubic metres per metre - i.e. square metres. The continentals use litres per 100 km as even they would find square metres rather odd.
Back to RT - I always described 'to' and 'for' (or were they 'two' and 'four') as the 'Dangerous Dative'. The US-style clearance 'climb / maintain four thousand' was better than 'climb four thousand' as it was unambiguous.
Oh - and the UK 'cran'? That was defined as 37.5 gallons of fresh herring!