So I'm looking for a bit of help with extending the fence on my early 90s Grizzly G1023.

Grizzly has not made a rail kit for this table saw for a number of years. Currently the saw has the original 32" rails, which I like to extend to 52" or longer. Otherwise I'm fine with the fence system, ever if it moves a bit when locking down. The rails themselves are a bit of angle iron in the back, angle iron in the front, and square stock bolted to that. I believe the square stock has been ground in some manner. It seems to me that I can just figure out the square stock, and angle iron dimensions, and have it cut to length.

Does anybody have any advice for making sure the square stock has a pretty close tolerance? Is there a particular type of steel that I should request? Is it possible to ask for it to be ground flat to further ensure it's reasonable flat.