[Rockdriller]

Jon,

All these answers are correct....
But, fer the record, the only blown head gskt I've ever had on a BBV6 was on my original 305E which I was happy to find out was just the rear block-off plate on the right hand head....a one hour repair.
I spent a few of my younger years as a "Mr Goodwrench", GM mechanic.
Any time we did in-frame work on an iron block engine, we would prep the block for head gskts by using a regular body shop flat board (manual, not pneumatic...) with 80 grit paper and just ran it over the head deck until all traces of the old gskt and any other impurities were removed...and then checked it like jimjaz explained.
A few shots of brake cleaner and a blast from the air hose and she's ready to go back together.
Back in the late seventies and early eighties, when I was turning wrenches for GM, this was the 'scientific' method recommended by the factory.
I guess they figured it wasn't rocket surgery.
BTW....I love the "Burbs"....we need to see some more pic's, I'm thinkin'.