I have the Hesco (Mopar) kit with the 4.2 head. It can be used either way but the manifolds must be matched to the kit you buy. I have heard good things about the Howell, but the Multi port is a little more efficient (and expensive) than the Howell TBI. It is huge advantage at altitude and big angles that challenge carbs.
1984 CJ7, 258, MPI, 4.0 head, Borla, 700r4, amc20 (detroit), Dana 30 (OX), 4.56 gears, Warn Hubs, Dana 300 with 4:1, 4.5 RE lift with 1" body, Bilsteins, dual battery, PS, PB, full cage, two dogs in the back....