there are a few builds here that have used the frame mount set up with a hydroboost placed further back on the frame. like under the box. they have used the brackets etc and then the rod, that would normally go to the booster to operate the system, was lengthened and ran further back to operate the booster in it's new location further back.
start on post 73 here
https://67-72chevytrucks.com/vboard/...=283107&page=3