4.3 liter vortec swap

my buddy has a 91 S15, hes got the t.b.i 4.3 liter, but he wants to swap in a vortec 4.3 liter fuel injected, not throttle body injected, like the 93 an up with vortec written in orange on the intake, does anyone know what involved in doing that swap? please, any info will help, thanx