Thank you kirky and malone.
Do not know what the 4 letter word for head could be but 30a looks
to be Z????A.
Not sure of parsing of 43a. But mouth of river ending in Y fits.
It seems extra letters have two numbers. Starts with 9 letter one and then has 8 letter one later on.
working on 27d, 36a, 45a. Bottom half only partially filled.