Doubt the mod motors have enough balls to spin 2 centris to any kind of useful RPM. Like most Centri blowers, the Rotrex's have a recommended power N/A in order to run the blower. You don't have to meet this, but your power curve will suffer (why you have to run alot of gear on a centri powered Modular)
Typically twin supercharged apps are 420+ CI Big blocks, however the Koenissg ( I know I spell that shit wrong) I believe uses these on a 5.0L motor
I went to their website and they have an Alfa Romeo v-6 engine spinning it so I don't see why not 4.6 v-8.
I was talking about in the Twin Supercharger configuration. These would be awesome for a single blower setup on the mod motor. They would allow people running other Centris to cut the gear way down, allowing you to stretch the legs more on the highway =-0
If you wanted to run small ones, I guess you could on the mod motor, but the engine bay isn't really setup for it, the crank snouts also aren't nearly as strong as BBC/BB Mopar, where twin centris are typically used in a race app.
Although like anything else it can be done, but is it practical to try to run 2 smaller blowers in twin configuration on the mod motor when they make singles big enough to give the mod motor all the air it needs and only drive 1 blower =0
To be honest, I would love to take a car like yours that is already setup making bad ass power with a centri and just swap the blowers and add one of their ICs and see what the curve looks like @ the same boost level. I'm not saying these are like "so much better" but I think they are a different type of centri and it would be a cool experiment. Theres a reason why all of the Euro tuners and supercar producers use these babies.