congrats on the truck, looks like it should be a lot of fun.
I'll warn you right off the bat that asking for opinions around will get you a whole lot of information, and not all of it will line up with each other, your budget or your build goals. You can can easily drop all your $1200 budget into the front suspension alone, or you can modestly update all your running gear for the same price.
Know what your end goal is so that every step you make is in the right direction. No need to blow the budget in one area and leave something "more important" crying for attention. Since you have the '65 you should be set for the widest options of parts either new or old.
Here is my shopping list for updating the suspension on my '61. I spent a few weeks searching for the cheapest options and this is what i ended up with. While she isn't rady for the autocross and not everything was replaced, I'm happy with what i have. Affordable parts now can be replaced with higher end products later.
Top-After, Bottom-Before
I found a power booster and master cylinder on craigslist of a '76 c10 for $25, wheels and tires on CL for $250