[MySons68C20]

Originally Posted by Accelo

For most street performance applications, a 10:1 final First gear ratio is usually considered optimal.
Unsure where you are at because of the unknown 1st gear ratio. You could get close if you have a tach and the speed in 1st.
Assuming your current ratio is 2;20 to 1 and the diff is 3.08 you have a 6.76 final drive ratio. Way too high for performance usage. However, the same 3.08 with the Tremec’s 3.27 ratio gets you to a 10.07 to 1 final drive ratio.

A TH200-4R overdrive automatic utilizes a First gear of 2.74, a Second of 1.57, a Third of 1.00, and a 0.67 Overdrive. With this transmission's First gear ratio of 2.74 combined with a 3.73 axle ratio, the final drive ratio >> yields a 10.22 (2.74 x 3.73 = 10.22)
That is the performance sweet spot. Many believe it's too low for the street and it certainly would be without the overdrive.
The first gear ratio matters a lot and because it takes little change to make a bid difference. Consider first the two Muncie gear ratios. 2;20 and 2:56. Finial drives are as follows;
Close
2.2*3.08 =6.7
Wide
2.56*3.08 =7.8

A full point difference in ratios!
A friend mine has the exact set up you have, Tremec with 3.27 and 3.08 gear in his Chevelle. He considers it too low of a ratio for the street. He changed his differential from 3.55 because he thought he was driving a tractor (11.06 ratio ) and didn’t like it at all. He considers the 3.08 barely tolerable and would have preferred a higher gear for first.
In review I am guessing you are not dragging your truck and just want a street-able ratio I suggest you aim for something in the 8 to 9 ratio. We are not 18 anymore, well I am not but occasionally dive like it. On a "Closed loop course!"
The Tremec is also available in more than one first gear ratio. Consider this as you can see the 3.27 ratio is really low, as far as first gears to, and it’s designed for more modern vehicles with higher final drive ratios.
I am including a chart with the different first gear and differential gear. The final drive ratios are given for first gear.
Happy ratios.

Tremec
3.27 3.08 =10.0716
3.27 3.70 =12.099
3.27 3.55 =11.6085
3.27 4.11 =13.4397

700R4/4L60
3.059 3.08 =9.42172
3.059 3.70 =11.3183
3.059 3.55 =10.85945
3.059 4.11 =12.57249

4 speed (close)
2.2 3.08 =6.776
2.2 3.70 =8.14
2.2 3.55 =7.81
2.2 4.11 =9.042

4 speed (wide)
2.56 3.08 =7.8848
2.56 3.70 =9.472
2.56 3.55 =9.088
2.56 4.11 =10.5216

Saginaw 4 speed.
2.54 3.08 =7.8232
2.54 3.70 =9.398
2.54 3.55 =9.017
2.54 4.11 =10.4394

Great info Accelo, thanks for the weighing in!
BTW, this site rules!!