I believe it is SRD, Though exceptions are sandstorm and the spell compendium. So SRD and sandstorm/spell compendium.
I was thinking more rocket powered sand sleds than mechs though.
Anyway, Using a port over of the craft mechanical skill from d20 modern, But I have to RP the experimental process Starting with a late iron age early Renaissance age technology.
I have to expend a similar amount of resources to develop and build something that it would take to get the closest magic item equivalent.
And finally nothing that is a total gamebreaker.
So, it looks like rogue with high intelligence is my best bet. So aside from skill focus is there anything I'm missing that would help out on building my fleet of airships and rocket powered sand sleds.