I think you can go ahead and finalize with TurboTax and they will hold your forms until the Hybrid Credit Form is available.

In the instructions for the OK 511CR (hybrid credit form) it states to attach "A copy of a paid invoice itemizing the cost of the equipment and installation must be furnished; including, if applicable, the type of fuel to which the vehicle has been converted." Does that mean manufactured cars as well? I was going to include a copy of my title if it was actually required.

Still happy with everything for the most part, even though I'm not getting all of the Federal Hybrid credit (about $400 short) I am getting the $1500 OK hybrid credit that I had not planned on initially.