1960 engine/trans mated. Engine wont turn. w/pics.

[paulkersey]

OK.
The stock bolts were already digging in and shaving so I thought some flat washers and locks would prevent further damage.

[The Tassie Devil(le)]

In that case, the flat washers would suffice, and the inclusion of lock washers won't have any adverse effects on the bellhousing material.

Lock washers are designed for use where vibration, and movement can be a problem.   As the Bellhousings are located via dowell pins, there is none of the aforementioned problems.

Bruce.