ditch the aircon,saves weight and power,stick to the same engine,they are cheaper,get the head flowed,inlet etc flowed for more responce,get a lightweight crank pulley wheel,new belts etc.. and just give the engine a full service.Get the suspension bushes replaced,even if cannot afford poly's,replace with standard.you will be surprised how better the car will feel and drive.Also include new engine and box mount in that.Do the airbox mod,with a free flow-filter in.At the end of the day,it should feel quicker,firmer and more like how it should drive,also your insurance will hardly increase.A proper set-up car will poss drive and feel better than one thats had ££££££ spend but not set up.