Hi, just of curiosity, what does a 4449 do, and who makes it ? Can you post the block diagram or logical equiv. I can't find a reference to it in any of my stuff, so of course I'm curious.
According to the documentation I have for the 8800b, there is a chip labelled "S1" on the display/control board that can be a 4009, 4049, or a 4449. The parts list has them using a 4009, MITS stock # 101143. There is also a 4009 on the CPU board, but it doesn't say anything about using alternative ICs. It does however have the note "ICs A and M (4009 and 8080) are MOS static sensitive ICs".
You might try searching http://www.alldatasheet.com/ and seeing if you have any luck with further information or possible alternates there.
Hope that helps.
Now a 4049 I've heard of. A MC4049 is a old-style CMOS high-voltage family hex-buffer. There's actually a NTE cross-ref, NTE4049, and at least Parts Express has it, they were the first I could think of that actually have them in stock.