Hi Vic,
For a 30-40S pack, some options if gauging is a key requirement:
(a) Gauge based on a subset of the total cell count, for example using the lowest 4 cells and using one of our already released devices (bq3050, bq20z75)
(b) Gauge based on an "average" voltage of all cells by taking the net stack voltage and dividing this down to the equivalent of a single cell. The recently released bq34z100 would support such an implementation.
http://www.ti.com/product/bq34z100
In both cases, the protection side of the BMS would need to be handled with a separate solution; the bq76PL536 that Ed mentioned has a native stacking interface and could be interfaced to a µC, in which you could implement the protection features needed.
Thanks,
Allen