Hey it's my electric beer symbol friend!
I see you are still losing sleep thinking of all the rubber you want to burn with electric power muhuahhahaa
My number 1 experience building has been not factoring, or even thinking about battery power.
I would take the budget you have explained now for controller, motor and throttle etc. and double-possibly triple that amount and thats what you will need in total for batteries + your machine.
How far do you want to travel in this?
If it's just for short runs you could get away with a minimum 48V power setup, but the current usage is huge - you will need to limit the controller. You mentioned a 'screen' available and there was one on the GM site but it has vanished (it was for the HPC300/500). I see they have put the new wheelchair controller on there too. Anyways maybe contact Tom
tom@goldenmotor.com and see if you can still get one. They were $380 or something from memory. Looks like the model number has to do with the current rating - 100B = 100-300A, 300 = upto 300A, and the 500 upto 500A.
Really depends on the $$$ you want to spend on batteries, you have pretty much all the parts in your questions apart from a frame
Wow people are really power hungry these days its fantabulous