Here's the link to the tech rules. > http://www.amrca.com/about/tech.htm
> Rulebooks > WMCR Rule Book
Track construction detail are on page 22 -26, but I did not see any spec for "flatness", or surface finish. There are a couple of "how to build a track" article and in them it is suggested that a transit be used to level the form work; you can get pretty tight with a good laser transit, but we're still talking "fractions", not thousandths of an inch. The center pole is required to be what looks to be 2" solid steel bar. Not a cheap hobby by any means. Check out some part prices.
Max car weight,depending on class, looks like about 6-1/2 pounds. The cable diameter is dictated by class and speed; ranging from 0.035" - 0.078" diameter. Increases in wire diameter, per class, are required when exceeding given speed ranges. Obiviously they don't change the wire diameter on the fly, it is determined by the speed they will attempt to reach.
Engine displacements: Class I @ 1.5ccm through
ClassV @ 5-10ccm
Weights: Class I; 2 pound, 5 ounces through Class V; 6 pounds 14 ounces.