You would use the bottom half of the 7MGE intake manifold, and weld a plate with DCOE spaced holes to it. The individual runners would need to modified. You would block off the injector holes with 12mm welch plugs. The you would need to buy 3 Webers and tune them and also modify a distributor (put the guts of a 5ME/analogue 5MGE into the 7MGE dizzy). Then you'd need to tune it.
It would actually work out only slightly more expensive going multi throttle body EFI. IMHO, the crispness of response and ease/stability of tune would be worth it.