Ive done haltec e6x to l20b, gets costly very quickly especially with tunes.
Ruffly 1-1.5k average computer cost + install if you hate wiring
Injectors, regulator, fuel pump all cheap enough even 2nd hand if you want cheaper stuff.
Manifold fabrication etc etc, id guess my conversion cost over 3k and id never do it again, that money could be better spent. Whats ya l20b like, pritty stock or worked?