Uh. Well. Erm. Doesn't gearing have to do with the tooth count on the ring and pinion? It doesn't change the actual size of it, just how fast it turns. You could put 4.11's in a 7 1/4 just like you can put highway gears in an 8 3/4. And yes, some of the carriers won't take certain gears. I believe with an 8 1/4 anything that came with a 2.71:1 ratio or higher (lower numerically, such as a 2.45:1) was a different carrier than anything like a 2.76 or lower (higher numerically). So if someone has 2.76's they can go 3.23's or 4.11's or whatever but if they had like 2.45's then they're kinda stuck with bad gearing. Maybe it's the same for the 7 1/4, maybe not, but I've never had to deal with a 7 1/4. When my car left the assembly line it had a 3.21 geared 8 1/4 rear end and a slant six. Maybe OP lucked out and got an 8 1/4 with a slant too but probably not. And going from a 2.76 to a 2.94 just seems like a waste of money for what you get out of it. 2.76 to 3.21 or something close to that would be better.