[ProStreet67]

My opinion 3:73's are a good set of street gears. Stock tires are usually about 24-25" in height depending on the tire manufacturer. You can look at several tire manufacturers tires in the same size range, then look at the actual spec sheet. They can vary in height from 1-2". Its crazy but true.

With the 275 tire you are probably somewhere in the 27" tall range. Going from a 25" to 27" tire, your final drive gear ration is reduced anytime you go up in tire height. So if your stockers came in at 24 and your now at 27, thats a 3" difference and that will make a big diff on final drive ratio.

Im running a 295x50x15 on an 8.5 Weld drag lite on my 84 SS Monte Carlo with a mild 350, turbo 350 trans ( No overdrive ) and a 3:73 rear. At 60-65 Mph im at about 3000 rpm. With an overdrive tranny, that would drop down to about 2200 maybe less.

In my Suburban on steroids with a 35" Tall Tire with 3:73's and a 4l80e overdrive tranny at 60mph im running less about 1800rpm as a comparison.

I would go 3:73's if your running a auto tranny with overdrive. Its a fun gear and the car will like it. My SS Monte is fun to drive with the built tranny and rear gears ( not as much fun as the Chevelle though ).

In the Chevelle Im running 4:11's with a 33" tall tire, that cuts the 4:11's down to about a 3:73 or so.

Word of advice, if you do change the rear gearing, let a professional do it, otherwise your asking for trbl, IMHO.