We have an all-GM injection setup on a 350....if you call a MEFI3 (mercury marine) controller being GM...... except for the air meter.
You can make or buy the injector bungs to weld into the ports of the manifold. Ours was based upon a Vortec-design block so the crank trigger was the stock vortec unit and used the toothed wheel on the snout. MSD makes a air meter that uses the stock holley pattern so it bolts to your manifold. Use a late model, computer controller distributor (smal cap with remote coil) to take care of the ignition. The major difference between a batch and a sequential is in the controller and the addition of a crank position sensor (to know if it's at #1 or #6).....ours is batch and for the street, it is fine. Sequential is probably a tad better for emissions and theoretically for performance but, for a street engine, is it worth the extra effort?

You'll have to add the usual return line or run one of the new returnless setups. IT is suprisingly easy to add Fuel Injection to an engine and it is worth it......we will never build another non-injected engine unless it is for a drag car where a Holley clone is appropriate.

mike in tucson