Have a look at the link below, has taken me some time to find a good workable solution for an injected Essex. I think this would be quite a good way of going injection on an Essex. Any comments or thoughts would be held in high regard.
http://marcosforum.org/topic/5379/Fuel-Injecting-the-V6?page=1
Capri

That is a way to do it, however I beleive that particular set up is over throttle bodied.  It has 3 feeding a single plenum, and generally that doesn't work well.
 
The simplest I've seen is to weld an adapter for a 4 barrel and use a holley style throttle body (sized accordingly).
 
Cheers
Woz