No, I don't. It would take a LOT of engineering to break even with a properly assembled stock front end, if assembled properly and reinforced with export brace and Monte Carlo bar.
This 68 GT350 had rotted front rails, and they were replaced with Dynacorn assemblies. The work was done one side at a time to preserve dimensional integrity. These assemblies will cost you $1500 for the pair, a lot less than custom framing would cost. They also feature the 68 1/2 Cobra Jet tower reinforcement, which actually had to be removed for this Shelby.
68 GT350 Restoration
If you really want to do some reinforcing, add convertible inner rockers to tie the rails together. Much stronger than aftermarket subframe connectors.
Ditto on the stock rebuild first. Then add in the inner rockers. There are a Couple other ways to go. Mustangs Plus makes a chassis strengthening kit which is close to the convertible reinforcement set up. works great and really stiffens the whole car. I used Miar Racing sub frame connector on my fastback. They are better than most out there because the weld in at two spots in the front and two spots in the rear so as to not create a fulcrum affect. They are also round which is stronger than square tubing once it is bent to fit the shape of the floor. They do limit side exhaust though and cost a Little more than the cheap bolt in ones. If you have the money or talent, do the Mustangs Plus kit
The design is not bad, up to a point, the rear end is very good, and the round tube has more torsional strength than more common square tubes, but the front end is poor. If the tubes came forward another foot, ending at the wide part of the rail, it would be far stronger. As it is, it terminates at the weakest point of the front frame rail, adding no strength at at in the front. That portion of the stock rail is so weak you could bend one with your bare hands. Had the connector bridged past that, well, too late now. I would have added the stock 68-70 torque boxes, and run the tube to the front of that. What you have right now is weaker at the firewall than a stock 68 6 cylinder coupe.