Found the reference: Sounds and their patterns in Indic languages, 2
vols. Cambridge University Press, 2014. (As it turns out, there are many languages without a length contrast, especially Tibeto-Burman languages.)
HHH
:
2 volumes.
(Cambridge University Press
India).
Bangla has lost the old length distinctions; I suspect some other Eastern Indo-Aryan languages too. There is a good phonological survey by Pramod Kumar Pandey that may offer more information. Unfortunately the reference is not available
to me right now. Google might help
Best wishes
HHH