Strictly, you can't do a proper stength analysis without more materials/joint info. The modulus of low carbon steel (and most other metals) is not much affected by thermomechnical history, so you can go ahead with material-linear FEA (details of joints, with undercuts as described by tbuelna will have a small effect, but can probably be ignored in terms of structural stiffness in a first/second pass).
At some point someone will have to decide on allowables. In the absence of any more information the only safe thing to do is use the minimum possible, which is probably annealed.
It is more complicated if you are sizing the part rather than just analysing it structurally. You can get a force distribution and then set thicknesses, etc., when allowables are known; however, very few real-world structures like racks are statically determinate. The alternative is to set some sizes based on known available material conditions, and specify material condition as well as sizes. This may well depend on post-weld heat treatment to regain quenched and tempered strengths, which will distort the part with this sort of low alloy steel. Advice from a metallurgist is advisable before putting too much time into it. An initial stick model with bars is easily adapted to new tube section properties and could be built and left with essentially guessed sections until more is known.