Between 1000 and 2500 rpm it will be difficult to generate a significant amount of power.
Have you thought about truck engines? They rev very slowly but generate far more torque than passenger cars. I don't actually know (there are some people here who do) but you'd be able to get something like a 12litre engine with 300bhp and 1500lb/ft of torque. It might be a little heavy for flying applications.
Cool project though.....!
<span style='color:blue'>"So my BM makes me a flash bastard? Then I guess you're just keeping it real from the seat of your nova?"</span>
<span style='color:gray'>"...and the home of the brave..... is bravey 130bhp from a 7 litre engine? 100bhp/litre or don't bother building it!"</span>
<span style='color:red'>"Aaahh the UK; where every road is jammed, under construction, poorly maintained and unfairly policed, at least we don't get over-taxed for it........ HA HA HA!"</span>