I don't think so. I checked Dynacorn, Scott Drake, Branda and CJ's and none of them offered a reinforced or big block tower. You might have to fab up some of your own reinforcements. Are you doing a Concours restoration, or a restomod and you just want stronger towers?
Have not seen them already welded to tower when you buy them. But you can get a reinforcement kit. I ended up not putting on mine - general consensus was not necessary when I upgraded to 347.
Only the big block Mach1's had the reinforced towers. Since you are not going for concourse you can buy the kit that Palerider posted and reinforce your towers. The kit includes pieces that the factory didn't include and it would be even stronger.