I was able to increase the resolution (I've tried 1280x720 and 1440x900) and luckily it doesn't stretch. It is Vert-, but it's not really a huge problem with this game (the car is a little closer to the screen and you see less of the sky) and because of the really low default resolution it looks very much improved.
Unfortunately the HUD is still stuck at 800x600 and I haven't yet figured out how to move it. So it looks kinda stupid, as you can see.
800x600 (4:3)
1440x900 (16:10)
I'm not certain how I'm going to be able to solve that problem. The (800x600) HUD elements (minus the tach) are located in a file called meter02us.txr in the BINDATA directory. The .txr extension appears to be a CorelDRAW format. I don't have that program, so I don't have any way of editing them. Simply deleting the file kept little white boxes on the screen where the elements are supposed to be, though, which leads me to believe that the screen coordinates for the individual elements are possibly located somewhere in the executable itself, but I haven't had any luck finding any of them.
Anywho, the resolution fix itself is quite easy.
You will need a hex editor such as
Be.HexEditor. Open your SegaRally2.exe file with it and search for the string
20 03 00 00 c7 05 d0 4d 4d 00 58 02 on line
00020930.
20 03 and 58 02 represent the resolution 800x600. Replace those with the resolution of your choice.
1024x600 - Replace 20 03 with 00 04 and replace 58 02 with 58 02
1280x720 - Replace 20 03 with 00 05 and replace 58 02 with D0 02
1280x800 - Replace 20 03 with 00 05 and replace 58 02 with 20 03
1366x768 - Replace 20 03 with 56 05 and replace 58 02 with 00 03
1440x900 - Replace 20 03 with A0 05 and replace 58 02 with 84 03
1680x1050 - Replace 20 03 with 90 06 and replace 58 02 with 1A 04
1920x1080 - Replace 20 03 with 80 07 and replace 58 02 with 38 04
1920x1200 - Replace 20 03 with 80 07 and replace 58 02 with B0 04
Then simply select 800x600 in the launcher (640x480 actually crashed the game for me; looking online it appears that it's a fairly common issue). The main menu stays in 640x480, but the game itself (along with a couple other screens) will use the higher resolution. Again, I've only tested it with 1280x720 and 1440x900.
I should note that I'm using the demo for this since I do not own the game. Hopefully the full version works just the same.
I'll screw with it more over the next couple days and try to find a fix for the HUD. Let me know if 1920x1080 works for you.
Oh and because of the two camera angles offered I was able to use a memory hacker and make some progress towards isolating the FOV variable, but didn't have much luck getting it to change.