Changing gears???

[nsmall]

Newbie changing gears.  So I have a mild built 340 with a rebuilt 727 slapstick with a rebuilt stock stall converter I'm looking for more traction and fun off the line.

I have an open end rear end with 276 gears according to the test I was told to do and the results said 276 gears.  I can often be seen spinning my passenger tire at stop lights.  I have big tires in the rear.

So for $750 I can go to a fresh seals/bearings 489 case used third member with used 323 gears and a sure grip.   I only get 10 mpgs now so I hope this isn't a major change in mpgs???  My current gears are a little weak off the line. So does this sound like a good idea?  I can chirp the ONE tire pretty good now, will a 323 sure grip still do a good burnout with a little power braking?  Will I notice a major difference off the line if I get 323 vs the 276 I have now?  If I want 3:55 gears the price jumps to $1250 as the guy only has new parts for a 3:55 third member.  I would even consider 391, but that may be too much gear.  I mainly drive in town, maybe 15% on the freeway, never race the car, just like to do a burn out every so often and want more power off the line as I like to goof around and go 0-60 quickly at times to give my son with autism a thrill.  Mainly just go on 2-4 miles cruises around town...my town has lots of stop lights so I mainly stay under 60. 

Thanks

[dfrazz]

3.23's are better since the 2.76's are basically the highest gear you can go, but if you want a noticeable difference off the line you will have to go down to 3.55's or lower.  However, your mileage will drop some and the RPM will obviously be higher and effect any highway speeds.

[burdar]

I thought I had already replied to this question...I had.  Try posting your question in only one section. 

Originally a 340 car would have come with 3.23's.  3.55's were an option.  I've heard a lot of people say that a 3.23 is a crap gear.  I had 3.23's on my Challenger for a short time but went back to the original 2.76's when I encountered some problems.  I didn't notice any change in acceleration but the rpms did drop on the highway.  3.55's are probably your best bet but mpg will be affected.  While the engine is out, you might also consider a slight bump in convertor stall rpm.