Why the desire for to buy broken Discos? Is it because you like the Disco and it's just a question of price or do you specifically want a project car?
I would avoid project cars at all costs if I was trying to buy a daily driver. The cost of maintenance, parts, and gas is enough to push any driver (and lets be honest, particularly a female driver) over the edge with an LR. Even if cost isn't an issue then the inevitable times that the car is down and you need to bum rides around town will blow. If your budget is only a couple grand, look into a domestic Jeep/Ford/Chevy truck. They will be far less costly to operate and probably less likely to break.
However, if you are stuck on a Disco (who can blame you?), try to find one that's cheap because of paint or body damage - basically anything besides engine trouble. While the seller may claim "blown headgasket", it could just as easily be a cracked block, slipped liner, warped heads, or anything that could lead you deep into $3K repair territory. Without road testing the car and seeing how it responds, there is simply no way to know what is wrong with the motor.
Good luck man.