My 60 Lira (.02 USD) worth...
       I agree with GMB, cinch the chain around the bell housing.  The taper
of the bell housing should keep it from coming off.  In addition, I would use
a little wire or coathanger (!) threaded through the bolt holes or twisted
around the prodruding bolts and tied to the chain to make double sure it
won't slip.  But that's just my paranoia talking.  I'm sure it won't fail.
We are talking about towing it on roads, right?  Not 4-wheeling through the
woods?
       I would be more concerned with what manner of filth will come flying
up through the open engine compartment!

Best of Luck

Bill Marshall
85 GL Tiico
Bradenton FL