Doesn't the Saab 4 pot derive from the Triumph 4 pot? I'd have thought that they would be similar in size, although the heads may make a difference, I suppose. I don't really know earlier Saab engines, only from about the B205.
Hmmm, this tells us a bit about the evolution, but not much about sizes and weights...
http://en.wikipedia.org/wiki/Saab_B_engine. From looking at the H engine stats (
http://en.wikipedia.org/wiki/Saab_H_engine) it may be worth looking for a B201 from about '82 on as this sounds similar in basic design, but has the benefits of higher compression