Not a lot of stress on those bolts so you don't have to go
lookin' for grade eight or nothin' like that. I would install
the bolts without the lock washer and grind the end if you have
to till the head touches the casting, then you know the bolt
will tighten down with a lock washer under it. Hardware store
grade five is plenty good for that application.
The ideal way to install the bushing is to use a driver that
pilots in the hole and pushes on the whole edges of the rim but
most people don't have those at hand or a way of making one. If
you freeze it as Fred suggested you have to have everything
ready to go and be quick about it cuz the minute it touches the
crank it will soak up the heat within a few seconds. In other
words get it tapped in with in a few seconds. should be just
flush or slightly below the champher.

DG

Denny G
Sandwich, IL