Its almost as easy to make a manifold for quad as it is for single throttle body.if you use motorbike Tb`s and they are relativly cheap.
A cheap but efective and fully adjustable ECU is the Megasqirt unit, i think they are only about $350 in kit form. There are members on this site that have experience with them.
EFI parts will soon be available for the A series through "Lagwagon". Including Quad throttle body manifolds to suit a particular bike quad throttle body, Crank trigger pullys for ECU crank reference and Modified distributors for Sync signal (required for sequential systems).