As above, if you fancy it do it I say, engines you can get new for C1.5-2k if it all goes T%%T's on you, have the car checked over by Nick at Austins or an equally qualified chap.
If you have any worries you can have the car remapped to produce slightly less horses.
Best of luck with the project...............by the way if your thinking about it you are already hooked Oh By the way it is said that the engines are good for 200,000 miles plus, and are good to take around 450BHP in standard form....................however it is said.......................all engines are as you know different.