Offshoreonly.com - "990" & "188" BBC Heads

In the middle of my winter rebuild project (which is snowballing like crazy) and one pair of my 990 casting heads has too much water damage. I doubt there's enough material left to hold the seat in the head. I'm having a very difficult time locating a set in stock form. Plenty of engine shops have them around here but they've had port work done for drag racers etc. I've heard the 188 casting is a replacement for the 990, although the info I've seen also shows it to have a slightly smaller chamber. Anybody got the skinny on these two heads or know the whereabouts of a pair of 990's? Trying to get this project in the water for 1st weekend in May. Can't miss the season opening Poker Run!