A few interesting points there
Is the E series actually lighter than the B? The E series is a serious lump of metal!
Austin rover did a V6 version of the V8 for the 6R4 but that was 2991cc , the first two prototype cars were still 2 valve heads the rest being 4 valve and quad OHC
Were the Australian v8 '1800s' front wheel drive?
Interestingly the V8 will sit on the 1800 gearbox with a few mods to the primary gears, I've seen a few minis in magazines using that arrangement.
BMC did two Austin three litres with Rover V8s but was considered too close a rival to the P6b
Were the v8 1800s ADO16 bodies or Kimberlys?