M1 rotovator

Hi everyone
I have just acquired an old m1.. with the lever to engage the twin belt drive.. no clutch!!
The engine... a Tecumseh BV153 has so many parts missing from it, that i have decided to bin it and replace it with another....This is where i need help and advice please.
What engine should i plonk on it.. Briggs.. Honda.. Tecumseh?? and what size of engine would be best?  It also only came with the two inner tines!! any idea where i could locate the outer ones?
Thank you.
Kinza.

Thanks bill.. getting an engine is not going to be a problem, like you say there are loads on the bay and also gumtree! I just dont want to put an under powered one on.
Would also like to find one that has the same sized keyed shaft so that the pulley that came off the Tecumseh will go straight on.
kinza.