[hat_man]

Thank you all for the help and information.

My drive to work is 60 miles one way on 2-lane blacktops with the occasional stop sign or light. I know there will be some loss when taking off from stop signs/lights, but I think I can make up for it with the longer stretches at 55 mph.

Using soD's math and the tire size calculator from Smurf, these are the numbers I am coming up with.

My stock tires (225/70/14) come in at 764 rev/MILE. If I wanted to go from my 3:73's to 3:45's by only changing tire size then,using soD's math, I would need to find a tire that comes in at 703 rev/MILE. (764x.92)

From the tire calculator these are my choices:
215/75/16 at 703 rev/MILE
225/75/15 at 713 rev/MILE

If I do the rear gear swap to 3:45 and want to get to 3:31, then using the same process I take 3.45 divided by 3.31 and get 1.04 as a multiplier. Using soD's math again I am now looking for a tire that comes in at 733 rev/MILE compared to my stock tires at 764 rev/MILE. (764x.96)

Using the tire size calculator again these would be my options:
225/70/15 at 736 rev/MILE
215/75/15 at 728 rev/MILE
195/75/16 at 733 rev/MILE

If someone could double check my math and I did it right, then I will have to take the next step and research which tire sizes are available from which companies and their overall weight and cost.

Thank you all again for all the help.