While I try not to directly discourage people from tackling projects on their own, I do often try to warn people about building the 4L60E. We're not talking about a Th350 here. The 4L60E was plagued with many "design flaws" from GM. Most tech manuals don't even address these flaws when instructing you to build it.
I see this all the time. I get stuff in here that is either ha;lf apart and someone got scared or something that someone built that either never moved or didn't make it very far. The biggest issue is, if you misassemble something, it can tear a bunch of stuff up and overshadow any money you were trying to save. Do the math real quick. Let's say you can find all the tools on Ebay for $300-$400, then you spend $400 on all the parts, you'll have between $700-$800 invested. We charge $850 for a "performance" build...With a warranty.
Now, here's something else to think about. Most of your generic transmission shops and chains even have a hard time with 4L60Es. Many won't give any warranty for "Performance transmissions".
If you're really Gung Ho about attempting this on your own, I'll try to help any way I can, though.
Frank