Old fire truck

Front

Rear

Hard to be sure because the pictures aren't parralle with the tires, but the only thing I see that concerns me would be the dual spacing in the rear. You should be able to slide your hand between the tires are the ground (lowest point). It is critical that the tires in a set of duals never touch sidewalls.

Now that we have some picture, although not great, the front drive axle center section looks like it might be a Clark 1530, which was made in several ratio's including 6.17 and was also made in both left and right rotation, so would fit a front driving axle application. A part number for the pinion gear would clinch it.
The rear looks like an Eaton, but the series would be hard to guess at. again pinion part numbers would help.
I have no idea what gearsets would be available, but the 1st order of business would be to nail done the make and series of the center section of both the front and rear axles.
Another possibility is a RA30 front and one of several IHC rears. Again casting numbers and pinion part numbers would help.

Not the best pics but all I have for today.

I might be able to do something with the casting number on the rear, the front we will need pinion part numbers to get anywhere. drop the driveshaft and look on the head of the pinon for numbers.
Alternatively you could pull the front cover off the front diff and look for part numbers on the ring gear.

Ok I'll get to it ASAP!

Before I get too carried away with trying to regear these axles. Do you think I'll gain enough to make it worth the investment? Also would gearing them up make them more reliable or better somehow other than giving me more speed and less RPM and possibly some fuel savings? The projected speed/rpm numbers with the current gears and trans combo I have in mind are about right for me. I think the only reason to consider regearing would be from a reliability standpoint.

Hold on here. Lets 1st id what you have, then you can see what is available and what it costs. Regardless of what you decide to do, knowing what you have now will help with whatever parts you may need in the future.
Your jumping two or three steps into the future. Don't decide to change until you have more information.

Wise words sir! Makes me think you may have done this before.