Dear Sir
You can use device FMB 120 that supports 2 analog inputs. Have in mind that your software needs to support 2 analog measurments fuel sum-up sensor whitch merges all fuel level sensors into one. Alternative you can use an LVCAN 200 adaptor and connect to CAN BUS in order to retrieve all data such as fuel consumption RPM engine temperature etc.
Any questions feel free to ask
Hope it help