£725 pricey
Yes, too pricey, by the time the lump is found there may not be enough cash left....
Like I said, keep it simple.

Get the basics sorted first. Get the lump in the car, coupled up, and connected to fuel, cooling, electrics and exhaust. Get some sort of engine management that will allow it to run.
Get a braking system working that will cope with the extra power/weight.
If it overheats, put a bigger rad. in. If it doesn't, happy days.

By this time you will have a totally different idea of priorities.
If it's too much of an animal, and there's money left, fit TC.
If it's a total scream and perfect the way it is, don't.
If it annoys you that the MID doesn't give you the right MPG, the sat nav doesn't work, the air con blows hot, etc, find a way to make it work.
If it's such a grin-inducer to drive that you don't give a damn how much fuel it's using, where you're going or how hot you are, don't.

Having built a car (albeit a totally different beast) I found that the decisions you make at the beginning (and which can potentially turn out to be expensive) don't necessarily get you to where you
later realise you wanted to be at the end of the project.

Take it in small, manageable steps and you can re-assess your aims and your budget as you go.
Kevin