Just picked up an Hpi vorza wing mount for 8$ shipped, and its almost a perfect fit for buggy conversions:
The width is perfect for the body mount holes.
You will need (2) 3x20 mm screws to run thru the front of the shock tower into the wing mount. There are lock nuts inside the hpi mount to lock it down.
You will also need a slight trim on the lower mount to clear the gear box(pic3).
You will need to then drill 2 holes in the tower for the lower mount, (2) 3x8mm screws and lock nuts thru the back of the tower to complete the bolt up.
This can work with the proline tower, but you can only use the top 2 holes for mounting(still solid, but weaker then the rpm and stock tower 4 bolt mount, and the stiffer proline plastic could maybe be prone to breakage with only 2 bolts holding it. I only have the top 2 in the rpm tower and it it rock solid that way.
This is the easiest buggy wing mount out there so far. PERIOD. Only thing that would be better is if traxxas or the aftermarket made a purpose built wing mount for the stock towers 4 bolt pattern.
Hope this helps someone 8)