Oh wow, I didn't realise that the suggestions had to be reasonable, or within a budget
In that case, what you should do, is rip the engine out and mid/rear mount a Rolls-Royce/Snecma Olympus 593 jet engine into the car.
As we all know, neo engines can be quite tricky to work on, and aftermarket parts aren't always that easy to find, i thought it would be far easier to bypass all that and just slot a Concorde engine into your skyline.
Some minor body modfications may also have to be done due to the dimensions of the engine being 4 metres long and 1.2 metres in diameter.
It's all worth it though as you will have 31,500 lbs of thurst at your disposal. That's without engaging afterburners, but we all know afterburners are for fags...