whoops - I meant one of the old capris (not that it matters). The thing about the tesla is the range and power output it achieves (vs the range of the leaf and others which generally get you only 100 -150km).Converting an older car up to this point would give u a similar result - a $16k conversion (with the older style lithium batteries) will give u around 120km - useless except for a daily commute to a local job (mind u the acceleration is as good as a petrol engine). The batteries apparently make up approx half of the total conversion cost.
You should be able to achieve a much better result with commodity cell technology used by tesla. They are apparently looking to sell an 85kw pack for under 20k, - much more respectable. To re-charge in 20min makes it extremely palatable. Makes it worthwhile owning an electric car in Australia (esp since we import 91% of our oil).