Lockup converter or not?

[phishfud]

My 84 K10 came with a 700R4 in it, and now that I will be doing a TPI swap, I need to know if it is a lockup converter or not. I really don't have a clue what a lockup does, if I need it, or if I have it. All my project vehicles to date have either beed TH350's or 4 speeds. When I get my custom harness, one of the options is for the lockup converter, and I just don't know what to order. Now my truck has had all the factory computer stuff and emissions removed by the PO, and there are a few wires coming from the trans that were cut. Truck runs and shifts fine though as it is. Any info would be great. Thanks.

Terry