A bit of car history:
No, not all mk2 RS2000s have the droop-snoot front.
Ford Australia made ones with normal flat front (and I think so did South Africa as well). I don't know if they were all badged as 'RS's, but certainly many were - I'm pretty sure the RS ones were all 2 doors, but they also made 4 door 2-litre Eskys as well...
I don't know about mk2s, but all 'export' market mk1 Escorts have stronger bodies than the UK market - very similar to the GT/RS body (type 49 shell).
Both drop-snoots and flat front 2-drs were homologated for racing as RS2000s.
All RS2000s in NZ are special imports, and there is a mix of UK, Austrilian, and home-made replica ones about...
On topic:
I haven't done it myself, but have considered it many times - there's heaps of sites with lots of detailed conversion info, try google (particularly the UK version http://www.google.co.uk).
Some people are now fitting the injected Serria motor, which I imagine would be great in an Esky.
The 5-speed is a cheap enough box and just as easy to fit as the Cortina 4-speed, and it will make for a heaps better end product.