How to model PCB Trace with RLC?
trying to figure out how I can replace a 4" trace with an equivalent RLC Circuit.


First choice: Don't. Use the 'tline' element in LTSpice instead.

Second choice: You can model a transmission line with a sequence of pi or T sections. If you use a different transmission line calculator, for example the Saturn PCB one, or this online one, they will output capacitance and inductance per unit length in addition to the characteristic impedance. 

Say your calculator says the capacitance is 1.7 pF per inch and the inductance is 12.2 nH per inch. Then you can break up your 4" trace into as many sections as you want. Each section of length L (for example L=0.4" if you break your 4" trace into 10 sections) will have 1.7 \$\times\$ L pF and 12.2 \$\times\$ L nH, arranged in either a pi or T circuit. 

Keep solving your circuit with this set-up, increasing the number of sections each time, until your results stop changing (this step is why it's easier to just use a built-in model than to try to make an LC model yourself). The higher the frequencies present in your circuit are, the more sections you'll need to achieve an accurate model.