MSD capacitor box replacement...

The 4 pin HEI modules are older tech, not multi spark and susceptible to low voltage death, and no rev limiting.
The 8 pin HEI modules are a lot better tech, but no multi spark and no rev limiting.
The FBO box is really only specifically for stock wiring (unless you wired it like the stock system was.) and has rev limiting.
The Rev-N-ator, but it also uses the OEM type wiring and connector and no multi spark, but has rev limiting.

The Pertronics Second strike carries a second spark throughout the RPM range like no other box, has rev limiting and CAO (crank angle offset) meaning you can adjust when that second spark happens depending on crank degrees.
Second Strike