The bolt dameter is 5/8" but the idea is not to pivot or align the engine on the bolt, instead it is clamped firmly between the frame lugs with the bolt. The inner surfaces of the frame lugs align the engine. So a precise fit of the bolt in the hole or in the frame lugs is not important as long as the bolt is tightened. A sleeve is not needed in my opinion. The distances on both sides of the engine are 1" long and has 1" diameter flanges against the engine case for support and added load spread area. 

When you tighten the front bolt, do that first without the gearbox rear bolt in the hole and check that the engine does not shift in the frame. The rear bolt has to slide in without effort and the gearbox lug has to be paralell to the frame lug. That can be checked with a feeler gauge.  If the bolt holes does not line up or you find that the gearbox lug is leaning, the frame needs adjusting.