my experience would indicate a clutch, most defenitely..
You can shift with the car off, and then start the car, the car lunges forward (the starter pulling it forward, and then eventually the engine lugging itself forward). This would indicate, to me, a broken clutch spring(s?) not allowing the clutch disc to disengage from the flywheel. This exact problem was just rectified via the wife's car, and it also ruined the nose cone, as well.
Clutch, nose cone, NEW REAR MAIN SEAL (~$20.00, CANNOT be replaced without dropping the tranny, again.. so do it while it is down, BEFORE it goes out..)
Search around your normal avenues to obtain a new clutch (make sure it has a new clutch disc, and pressure plate in there..) and be ready to have to pay for another smaller piece (nose cone, etc) if it did happen to get ruined (not saying it did...)
If you can't get a good price, Contact STEVE at Tousla Ford, and just mention the SVT plan. He hasn't stated that it is for SVT owners/cars only.. he specifically told me that anyone with that number would get the ~55% discount from list price.
Also try Bill Jenkins at Signature Lincoln Mercury, in Nevada. He is able to offer ~33% off.
(his number is VERY popular.. search troubleshooting for "bill" and "1-800" and you'll have it.
Steve at Tousla is 1-800-328-9552.
Shipping is normally around 3 days. (order Monday evening, have it by Thursday evening)
Ray