Yeah JohnB, hang on around here. Others here do use horses too. As you say they give daily youth-chores training. Best rubarb fertilized ever. (and as I tease my horse-lover sister - can be needs-must, eaten - we’re not WASP genes - but german/russian/native american horseflesh eaters)
On your 240/300’s, I and family have used these much in Ford pickups. Wonderful long life. Gear drive cam with NO Gm/Dodge CHAIN stretching.
I have woodgas operated these on big Onan generators too. Just as said will be a wood-fuel hog at full out 20-30 kW electric loadings.
Fellow named wgc1444 on youtube shows this. Read the comments feed back section there too, for his use details.
Down speed ran loading for best/fuel/wear efficiency you will want to engine operate at 1200-1500 rpm on these. Give the oil and coolant flows with minimal pumping losses. 800 is too low and will engine wear faster, loaded down.
For 6kW electrical you could belt drive off the engine front. That’s cheap to set up for.
Beyond that @15hp. You really need to power drive off of the engine rear. That gets expensive to set up for.
Regards, JIC
Steve Unruh