You'd be limited from obtaining the full potential from a 76 by the Vne limitation, wouldn't you? I recall it became quite restrictive above 4000 ft. I ferried a 76 A++ from Redhill to Lagos once, and wanted to use warranty cruise power during the high level Africa legs, but couldn't because of this.
With the EC-155 the fuel flow is fairly constant at MCP until you get to about 5000 ft, when the transition from Tq limiting to N1 limiting occurs, then it falls away dramatically. 330 kg/hr at SL drops to about 280 kg/hr at 8000 ft. I can recall the endurance reading about 2:55 on take off, with full fuel (1000 kg,) then showing 3:30 at top of climb! Combined with a significant increase in TAS with altitude, you could really stretch the range.