Dazzaute I am not quite sure how much, probably a bit more but it was just a conservative estimate. But where the weight is along the wheelbase also has an effect.

The computer is probably the most expensive thing, but that is assuming that you go injection. If you use a simple SU style carb on a suck through set up, it will be quite cheap. You should be able to get a turbo for less than $200. If you can do the work yourself, a rebuild kit is $100.

Good luck