Based on your question, Iām assuming you donāt want to just drill new holes that will line up. So if you take a look on the Vex robotics catalog page, under structure, you will find a variety of gussets including āpivot gussetsā (near the end of the page, in the gusset pack) which have slots in them allowing you to make adjustable angles in your design.
Gussets - VEX Robotics
Once you have the angle set correctly, you can usually find a place to attach a 1x bar or 1x1 angle, as a reinforcing strut, where a couple holes will line up.