OK first, you gotto know, that the 30 to 50hp is a pretty big step for a 273, and it's gonna come at some higher rpm like close to 5000. Below 2000 the power may be negligible, and from 2000 to 3000, the power increase is only gonna be 30 to 40 percent of the increase at peak.
Now;
5000 rpm with 3.23s and 77 inch tire roll-out (24.5" tires), will be ~38mph.
3600 will be about 28mph.
So, you will feel the power (with 3.23s) beginning at 28mph and peaking at 38 mph. then dropping off to the shift-rpm.
Is that what you want?
More likely your car has 2.76 gears, and the powerband with those will be 17% higher or from 33 to 44mph.
If you want the powerband to start at a lower mph, then you will need a higher stall TC.
Here is a power curve from a 5.2 magnum. Ignore the numbers. Just look at the shape of the curve.Notice the power at 1800 versus 2800.
Your current TC might be stalling as high as 1800. On this graph that is 90hp. At 2800 on this graph, that is 160hp, or 78% more. This is a serious increase, and it's still the same stock engine. It will change completely the personality of your engine.
The next performance increase would be rear gears.
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