Whether you are interested in racing cars or not, buy and read
(several times) Carroll Smith's "Engineer to Win". It contains the
best layman's introduction to metals and metallurgy that I have ever
read. When you are done you will know how to heat treat 4130, whether
you need to do so, and if so whether to do it yourself or to have it
done professionally- But you may also decide that you don't need to
use 4130 for your purposes.
Bob S.