Are you starting the car in neutral? I wonder if bellhousing is not aligned to crank centerline. If far enough out of alignment, maybe the pilot bushing is dragging and spinning the main shaft? Are you sure the clutch is releasing when pedal is depressed? Don’t know how new all the combination is. Is this something that was all together and ran/drove at one point or all new? I recall different length throw out fork studs but been too many years ago for me remember what is correct.
