I went ahead and got a millers falls 13hp OHV single to replace a B&S side valve.
fitting had a problem with the keyway in the mower drive stack pulley. while the crankshaft has a 1/4" keyway, the pulley has nothing. Originally there were a row of rectangular punch marks on the tube between the pulleys, These would have protruded into the tube and engaged with the crank for a positive drive. It would seem they they do not last. I have a 1/4 whit worth thread tap. So I drilled a series of holes along the pulley stack, threaded the 1/4WW and spent a $1 on some grub screws to engage in the slot on the motor crank.. A New pulley is $120. Nice win for once.
Fitting the engine was easy. The mounting holes lined up perfectly. I should mention that mount holes on these engines do not come tapped. The bolts holding the original motor may have a threaded taper on the end. These are self threading bolts. Easy enough to do before motor install.
with belts tight, wiring, oil and petrol, dont forget the throttle cable.
Before running it might pay to check bolts and especially tappets.
Mine were too tight, specs in handbook.
Motor started very easily, ran for 10 min or so and drained oil.
there where some little lumpy bits, new oil and all is good.
This is a victa/murry mower. the new motor will not fit under the bonnet. looks a bit naked without the bonnet, have fitted a bumper of sorts for the trees here. Time will tell about how good the Chonda is?