Excellent choice on the suspension upgrades! Some day I hope to do the same. As you know we have twin cars with the same wheel and tire package. I've been mulling the MTF minitub as well but may just pie-cut and reweld the area where the tire rubs on the front inside wheelwell to get me by until the suspension upgrades. Keep us in the loop on how the install goes!
Regarding the 7/16" for Vintage Venom, one thing you may consider is swapping out the VV bracket and spacer for the Mustang Steve brackets. Those have a 2 piece offset caliper bracket, which avoids the need for the 7/16" spacer for caliper alignment. You'd be $200 into those brackets, which has got to be easier than shortening your axles and tubes (plus pulling all of that and getting it to a shop).