It my 73, which is just a little 500hp small block, we are constantly breaking the drivers side motor mount.. I would guess at least 1 per year with the amount we street drive and race...

I've made a little torque strap using a hardware store turnbuckle set up and the motor mounts no longer breaks..

73 Duster 360 stroker
http://www.cardomain.com/ride/2594657