The consensus seems to be, that a multi-edition product would be best served by a minimalist stat-block, with the remainder of the information folded into the descriptive text where applicable.
I think then, I'd just cut the stats to only the ones that appear in all editions across the board.
Number of Attacks:
That's really the core of any monster information. Then all other stat information is woven into the monster description. Special attacks or defenses, magic resistance, etc....
Of course, now I suppose I'd have to give armor class as both ascending and descending numbers.
Hmmmm, now I'm more inclined to just stay with standard AD&D stats anyway. AD&D really is the Rosetta stone of gaming.
I have to laugh, I've done this many times before. Reinvent the wheel, or climb that mountain and find that Gary Gygax is already there, waiting for me.