CRT.5 newb questions

[jnev]

So, as some may have noticed from my signature, I have started a CRT.5 project. What is different about this project though, is that I will retain the stock chassis unlike most who upgrade to an Ofna, RCM or similar extended chassis. The reason why I will keep the stock chassis is so that I will have a variety of different sized rc's to choose from when I drive my rc cars. Because the truck will be about an 85% basher and 15% track car, I need a set up specifically for this. So now on to the newb questions:

1) Is there a smaller spur gear available such as a 44t?

2) What is a good weight oil to put in all the diffs (F/C/R) to get maximum performance on all types of surfaces (asphalt, sand, gravel, grass, etc.)?

3) I have 50 weight shock oil in the front and back at the moment, but it seems way too soft in the front. Should I move to 70 weight oil (only weight oil I own above 50) or is that too thick?

4) How does this set up sound...? Mamba Max ESC (already own), UBEC (already own), Lehner XL2400 motor (already own), Hitec HS-5245MG servo , Max Amps 4s2p 5000mAH pack

I'll probably end up with more questions, but thats all for now. I'll post some pictures of the progress, as soon as I get a chance.