I do not think you will get 70 HP out of a stock (1600CC) engine.
I bored and stroked mine to 2180CC to get 75HP from it.
Granted I did keep the compression ratio down so that I could use auto fuel.
I am turning the prop from the pulley end.
I worked with Great Planes to put in a special strengthened crank and bearing to put the prop on the pulley end.
Biggest drawback is I have to hand prop it.
Main reason I went this way was because I had the mount for this set up.
If I were to do it again I would put it on the flywheel end and avoid the hand propping.
You wil need to make a bed mount if you put the prop on the flywheel end.
If you are going to Mentone you can take pictures of at least one in the museum and get ideas.
Good luck.
Rick