Thank you both, I have decided to just use a set of parallel resistors for the part of the output.
I have found some really fast ram that works at 5V the 71256SA12TPG (
https://www.digikey.ca/en/products/deta ... PG/2011023 ).
There are a few questions that I haven't worked out the answer yet, mostly because I haven't investigated it nor actually applied to look into it.
The most important question: Is it possible to use this ram with the 6502? (or its 16bit successor)
If the answer to that question is yes, preferably an unqualified yes, then the next question is how to make it work for both video and cpu.
I have seen the idea of dual port memory, but I haven't found anything that is particularly satisfactory. I would like to be able to spec memory that can be as fast as possible to allow for flexibility later in per pixel times.
So one thought I had was to have effectively a double buffering going on. If the video memory is effectively 32kbytes, then I would have two chips, and would swap between them on the low bit of the counter. In the period of time where it isn't accessing one of the chips, another chip can transfer the video memory over from main memory without taking too much cpu time away.
That is the high level idea I am thinking about without specific means for doing any of it yet. So it might turn out that I can't do any of it or some of it for some reason or another.