First of all, you need to clean and prepare the surface for welding. De-greaser and a sandblasting shot is a good way to prepare le surfaces. But wire brush can also make it.
The easiest part is this plate, it will hold the vibration and dissipate the stress. Spot welding at 1cm spacing is good enough ( if your penetration is good ). Because you don’t want to reduce the strength of your sub-frame itself by weld it too much. Welding too much can reduce the capacity of the steel, please refer to a professional welder if you are not 100% sure of what you’re doing.
Now Time to tack every single parts in their positions, use clamps or bolts to hold the parts if needed !
You can now finish to weld everything in position. We used a MIG welder at this step to save a lot of welding time compared to a TIG. ( Again, do not over-weld, it can reduce the structural strength of the sub-frame itself ).
In bonus you can now weld these original points to reinforce it even more !
You can now paint your fully reinforced sub-frame ! In our case, we will fully finish the sandblasting process on the new reinforcements to get it powder-coated for a lifetime durability.