Some of the popular gear combos for MGB... "Column X" shows the product of first-gear ratio times rear-end ratio, and I included it to show how close they are. Ratios are approximate. I know this has been hashed out many times, it but might help a newbie.
<table border="3">
<tr><td> </td><td>Variants of Borg-Warner's T5 5-speed</td><td>First gear </td><td>Rear end </td><td>Column X</td><td>OD ratio </td><td>Overall ratio in OD (fifth)</td></tr>
<tr><td>1 </td><td>Camaro V8 T5</td><td>2.95 </td><td>3.9 (stock) </td><td>11.51 </td><td>0.63 </td><td>2.46 </td></tr>
<tr><td>2 </td><td>Ford Mustang V6/V8 T5 </td><td>3.35 </td><td>3.31 (MGC) </td><td>11.09 </td><td>0.68 </td><td>2.25 </td></tr>
<tr><td>3 </td><td>Chevy V6 T5 or Colorado MA5 </td><td>3.75 </td><td>3.07 (V8) </td><td>11.51 </td><td>0.70 </td><td>2.15 </td></tr>
</table>
(Note: I took the liberty of reorganizing Jim's info into a table with cells outlined. This forum trick is explained here: http://forum.britishv8.org/read.php?1,146 -Moderator)
This is very good information. However, now that I've reorganized the format of Jim's information slightly and can comprehend it better, I'd like to add that I used the combination in row 1 for a couple years and found it unbearable. So, I kept my T5 tranny and replaced my rear axle to go from 3.909:1 (stock MGB rear axle ratio) to 3.27:1 (in a Ford 8.8 axle.) I find this combination suits the torque curve of my Buick 215 better, and of course it provides a substantially lower engine rpm at highway speeds which is quieter and saves fuel. The change to a narrowed American axle had a another benefit: a cost-effective limited slip differential.
Thanks Curtis, I had trouble formatting because it kept changing different than what I was seeing.