Regulator/ rectifier

[LEE1969GB]

I am trying to get 2 rotax 793 engines in my buggy in time for an event on saturday and sunday which is quite a challenge but one problem I have is I only have one reg rec (I assume thats what it is) it looks like a universal one blue in color with 4 terminals. It kept the battery charged just fine when running it with one engine but the battery will need to power 2 fans to keep the engines cool and part of the event is at night so I will need to power lights as well.
Not sure what to do just use one engine to keep the battery charged or put the wires from both engine generators to the one reg rec, or could this burn it out?
I have a reg rec from a 20hp honda v twin engine could I adapt this? if so what am I looking for? which wires go where, I have a meter.
Any help would be great, With a bit of luck I can get it out this weekend but loads still to do.
Thanks Lee.