Its mentally easy but time consuming...

Lock the dissy to eliminate timing advance, run a J-pipe setup (dont have to make any manifolds), use a SU carbie as there easy to tune and your done...

On a stock A12 it will be the easiest 150hp youll get... and a heap more torque than a big dollar A15 twin carb set up...

I did it on an A12 and with about 14lbs boost and made 96kw atw... I did make the manifolds though but was a huge job to make them...

1st word of advice, dont over do it, keep it simple and make it work first... then try and improve on it... to many people try and make a world beater and never finish them...