SB vs BB who wins?

I have 1 more 73 400 block, I'm going to try grab a few more if they come up.
1 has a mainline crack and I use it for mock up but I'll do some experimenting with it also in the future.
I'm going to build the best of the 2 and hook up a friend I met on here with the other 400. Any idea what the limit is one boing one out? I try to bore as little as possible and I intend on sonic testing them as soon as they get here but figured with your experience you have a good idea.