Realisticly. On that budget your looking at cams or bodies. Your budget wont stretch to S/C / turbo.
Lets take S/C for example. That 3.5k at a stretch will buy you an SC and fitting kit . But then you want another 2/2.5k on top for LSD / brakes / good suspention set up blah blah. So on a 3.5k budget you could do an SC but it wouldnt be very drive able
where as it you do bodie you could have a well set up drivable 6 for 3.5k
my opinion anyway
Oh and realisticly your not going to buy a decent turbo set up for £3.5k
Lets take S/C for example. That 3.5k at a stretch will buy you an SC and fitting kit . But then you want another 2/2.5k on top for LSD / brakes / good suspention set up blah blah. So on a 3.5k budget you could do an SC but it wouldnt be very drive able
where as it you do bodie you could have a well set up drivable 6 for 3.5k
my opinion anyway
Oh and realisticly your not going to buy a decent turbo set up for £3.5k