Good Excuse

[NO_H2O]

There is no seal at the pully normaly. You can put a sand seal there, either push in or mach. in.
I have known some folks that have done this on street cars due to case pressure build up.
If you are going to build an egine I would do it your self, that way you know what is in it and if it is realy balanced etc. I'm sure you can find some good builders if it is beyond your tool/skills/space but do your homework. Don't just buy from someone because of thier add in a magazine. I have read some horor stories about a couple of builders that run big adds in magazines. A long block isn't that hard to build, if the machine work is right it should be a drop fit.