You'll spend a fortune building any engine.. a lot more than 5k if done properly. And I'm just talking the tall block, let alone any manifolds etc.
Cheapest way seems to me is buy a MK1 FRS engine, £2500 with gearbox and all ancillaries. Swap the turbo out and will do 300hp+ all day long on standard internals. However, not a very light engine having a cast iron block. You would have to swap out for a newer engine using an alloy block. I seem to remember that years ago my old FRS engine came on a pallet with a tag of 151kg, all ancillaries but no gearbox. The MTX75 I would guess is about 35-40kg. This is all without fluids too.
Boosted Honda engines have always been difficult to keep up with as they flaunt a steel bottom end, add some boost of circa 5 psi and they reach 350hp without a sweat. Just got to hope whoever calibrates/maps the ECU really does know what they're doing as it's got to be spot on for a high compression with forced induction.
Last edited by moondustka; 26-09-2016 at 10:32 AM.