You didn't mention what bodystyle your Barracuda is. Fastbacks and convertibles have more weight on the rear axle than the coupes. As someone else has pointed out, bigger tires on the rear are what you want if you're going racing, or if you want "the look". Putting bigger tires on the rear pretty much makes your car a fair weather driver. Any sort of liquid or moisture on the road means the rear end of your car is going to lose traction. Are you a big fan over oversteer or "loose" as the NASCAR folks call it?
Yes, bigger tires on the rear mean you've got a slightly bigger contact patch between you and the road, but looking at pounds per square inch, you've got LESS. Same weight, bigger contact patch, less force per square inch of the contact patch. This will REALLY bite you in the *** if the road is wet, or even if you drive through somebody's oil leak. Going in a straight line, you might get away with it, but if you're even THINKING about hustling the car through a corner, anything other than a bone dry road will just about guarantee you'll be able to see all around where the car is taking you, because as it's spinning, you're not going to catch it, and you'll just be along for the ride until it stops spinning. Either because you've spun out in the middle of the road, or because you've pile it up on some solid object (or another car).
All of this applies to virtually any Abody. The '29' bodies are the worst in this scenario. That fastback body is just a giant mass of air contained within a sheetmetal envelope.