Yes buy the Escort as £3k for a 2 door is a billy bargain, as long as its all solid
No do not stick the cossie motor in it
It will be awful, having a car with more power than the chassis can handle means you can not drive it hard without always worrying its going to spit you out and driving with that in the back of your mind just means you end up hating the car.
Personally I would say up to 200bhp of N/A power is ideal and will make for a proper fun driving car that you can drive with confidence.
This is why MkIGaz can run a 12.8 in his N/A YB Powered MkI and there arent many Cossies that can get near that time