Mason - as I am sure you are gleaning from all of these responses is that you need to take this in stages, first try and determine what is wrong before throwing parts at it. Some of who have/are building these cars automatically start fresh and rebuild everything so we know where we are, in your case you are doing it "old school" because money is an issue, thus you need to approach this methodically and with purpose UNLESS you are planning on completely rebuilding the entire car (which it does not sound like you are doing).
Think about it this way, there is what you need and there is what you want; if you are driving it then go after what you need. As time goes on, you can chase what you want.
As to welding the K member, I completely agree with doing this IF you are going to be running fatter front tires, driving it hard, etc. It is not something you HAVE to do right now, however I can tell you with 100% certainty that with even moderately fat tires in the front (probably even stock) the box will flex on the K frame. Firm Feel has a sector support kit to help this situation ($135 and bolts in). I do not think it completely fixes this but I am sure it helps and does not require any welding.
Since you are 18 and have jumped into the classic car world with both feet (which is excellent by the way), let me share a little information with you; there are lots of ways to accomplish any given situation usually and there are lots of opinions as to what is the best solution or path, you need to determine what best meets your needs and circumstances. It is very easy to get "mission creep" meaning you need something simple but then see all of the cool "better" parts and what should be a low dollar fix becomes a monster. Every car guy on here has been through this; you hear about it all the time where a guy started a "light" repair or refresh and now it is 10 years later and the car is blown apart with no end i sight. IMO the best thing you can do is fix the car has you drive and enjoy it, its what I did growing up (when no one was restoring these things because they were 2-8 years old).
Enough preaching, I am glad to see someone young get involved into the hobby.