Terminal blocks (solder lugs on the back, screws to hold lugs on the front) are available, though not usually from global distributors (IIRC, Digikey's catalog is pretty thin in the >50A range); you'll have to do the old fashioned call-a-sales-guy routine with a local electrical distributor to see if you can get some samples for a modest price.
Brass bolts are okay, and yes, as mentioned, they do need to be large to manage the resistance and heat (and, by the way, don't discount contact resistance -- it's probably a bigger deal than bulk material resistance, unless the bolt needs to be quite long).
If you insist on designing the connection yourself, the best method is to avoid current in the bolt at all -- connect the high-current terminals to a heavy copper block, and bring that out to the front. Then put a bolt through that, to clamp on whatever lugs are needed. That way, the bolts don't need to be special at all; they can be mild steel, for all you care!
Tim