What type of truck do you have?
Based on your user name, if you have a 1953, Patricks Speed Shop makes the 3:55 gearset and rebuild kit. This kit can be found at almost all the online truck sites. Shop them around or contact Patrick Directly and get the gearset and rebuild kit from the cheapest vendor.
The swap itself can be intimidating but taking it step by step with a high attention to detail, it's not too bad. I have done 4 sets to date so I've gotten pretty good at it. Feel free to send a PM or email with any questions. You can check out my WebShots page. When I did the first set on my own truck, I tried to take as many pics along the way as possible.
