LT1 engine swap-going from manual to 4L60E tranny?

I recently bought an LT1 out of a 97 firebird, and I am currently installing it into my 95 C1500 2wd extended cab pickup. My truck has a stock 305 with a 4L60E tranny. I bought the engine complete with the entire harness (which is still pretty much connected to everything), the accessories, and the brain box. Now I'm nearing the finish line, and it didn't dawn on me until now that there was a clutch on the back of the LT1. My LT1 engine harness doesn't have the big gray plug for the automatic tranny (which I assume connects to the shift solonoids and makes the transmission shift). How can I get this to work? It can't be that difficult, unless there were different pcm's for different transmissions. Can I use the current plug on my automatic tranny and wire it in? I'm not the greatest with wiring, but I can understand the diagrams if I study them long enough. Any help with this is greatly appreciated.