Adding a turbo to a N/A engine won't gain you that much performance increase because you wouldn't be able to run with much boost. Turbo cars have much lower compression ratios than N/A cars so they can handle quite a bit of boost. With a N/A engine you could only add a little bit of boost before running into problems with detonation (pinging) which is really hard on the valves, pistons, cylinder head and spark plugs.

Turbo cars also have special sodium filled valves which are able to withstand higher temperatures in the combustion chamber. N/A engines don't have those kind of valves so turboing a N/A engine will probably result in burnt valves before too long.

If you want a real turbo then you'd have to replace your pistons with low compression turbo pistons and the valves with sodium filled valves but that would probably cost you more than the difference between the cost of buying a Turbo car and what you'd get selling your car. Or you could try and find a turbo engine from a wreckers and replace your N/A engine with it. While you're at it pick up the Turbo exhaust which is bigger diameter than a N/A car exhaust.

All things considered you'd probably be better off and money ahead if you just sold your car and used that money to buy a real Turbo.

Just my $0.02 worth.

Roger