The first thing you have to do is rule out a six. the Escort engine bay is not very long, therefore to run a six it would mean cutting out and removing the firewall and radiator support panel. The next question is, do you want to stick with a caveman style v8 with holley carby, edelbrock manifold, powerglide, nine inch and 4.11's (the same as every other tom, dick & harry) or do you want to be progressive. There's a guy called Peter in the RS Owners Club who has a 2.0 litre Zetec in an Esky that flies. I can help you get in touch with him. Something like that, plus weight reduction, hilux or VL turbo diff, a reasonable sized turbo and dry ice intercooler setup would be my suggestion. There's a guy in Ballarat, Andy from Specialised Power
Porting who would be a good bloke to speak to about this or Rod at Motorvator Race Engines in Bendigo.
Or you could read my signature and give Frankie a call, tell him I sent ya.