If you are clever you could do it as cheap as $300.

$100 junkyard turbo
curved exhaust pipe with welded flange for turbo
Dump pipe back to tail pipe
Rubber fittings and pipe from compressor to carburetor. Make a Top Hat
Regulator & 15 psi fuel pump

Of course, the most important part is to tune it right. Make it rich is the easiest way to avoid lean-outs. Larger primaries and fit a large power valve. Retard the distributor and limit the mechanical advance. It'll have a bit of lag, but make excellent power under boost.

See "Stage 1" in the Turbo article.