30 - 40 kW aint happening @ 1500 rpms on woodgas. 300 ci might be able to maintain 20 kW and 25 kW at best. Torque gets you going, horse power keeps you going and there is just is not enough ponys available on the producer gas to maintain much more. The torque on the other hand I bet that engine hardly flinches when heavy loads are applied. If I ever build another V8 machine I was planning a L31 383 Chevy for that reason. But I dont think I will go back to those large machines. I think the teamed machines will make them obsolete plus they offer many more advantages. The Italy machine with the 5.3 ltr the client said it could pull 30 kW. This is an engine thats 45% and has a lot of performance gains over the heavy industrial beast.
Edit: so yeah it puts out roughly 60 hp @ 1500 rpm. Now factor in the power losses running producer gas. Yeah that puts it somewhere in the 30 - 35 HP range. So roughly 15-20 kW capable continuous.