larger H-bridge for any rc servo

[spankedchrome]

I'm looking to add a larger H-bridge /s to my servo/s , The only problem is I don't know where to begin my search for the PWM signal/s (forward/backward) and I also have not done such a thing before and don't know the intrument to use . Can you help or paste a link in the right direction ?.
Here's a link to where I got the idea from , not that I 'm into the hobby in that way (sandrail?) .

http://fp.enter.net/~rockcrawl/servo.html

http://fp.enter.net/~rockcrawl/buggy.html