Welcome to the forum Mike.
I'm guessing you are using Lithium chemistry as the primary battery source, is this correct?
Normally, you only measure the voltage of each cell in your battery pack, using a board such as this BMS12 from Zeva.
Zeva is here in Australia and the small company operator has converted a number of vehicles including an RX7.
The guy there, Ian Hooper is very helpful and seems knowledgeable in both electronics and electric vehicle conversions. He even converted a mobility chair which is able to perform wheel-stands.
The BMS12 board is a CAN bus board and you can set the CAN address of each board thus allowing you to string a series of these boards together.
The board offers programable settings for each cell, for example, under volts, over volts and the balancing threshold.
I've looked into using this board for a different situation, my off-grid renewable energy system, where I am installing 400Ahr at 25.6 volts of Winston Yittrium LiFeYPO4 cells.
I have an Arduino DUE which has CAN bus already built in, and just needed to buy a a few little CAN bus transceiver boards.
The DUE will be CAN bus master and communicate with the BMS12 to get and set data.
Is it possible that you use such an idea to get the voltage reading you need?
Then for the current sensing, you can use a number of methods, but for being able to read up to 1000Amps, maybe a good sized current shunt with an op-amp to feed back into the system, via CAN bus.
I use hall effect sensors, but in the order of 50 to 100 Amps, and so these won't cut it in your case.
I started to have a read of the thread, and can (no pun) see it details many things over many pages.