Can not rotate converter on C4 application, although there should be movement as mentioned. Converter studs protrude thru the flexplate during install.
Is it possible the converter was bolted to the flexplate first , then the trans installed on to the engine? If so... broken pump is the result.
As it sit now, sounds like a broken pump may have happened
At the Bonneville Salt Flats, first gear is known as 130 mph.