The Tie bit is from the original 1978 MPC Darth Vader TIE Fighter model kit. The Harley bit is from the Tamiya 1/6 Harley Davidson FXE1200 AMF Super Glide, however the sprue that I bought was (apparently) from a Tamiya 1/6 Harley Davidson FLH1200 AMF. From what I can tell by looking at both kits, they have some similar parts, so any of the 1/6 kits that are like these two should have the correct sprue (Sprue C). Heard about it from RS Propmasters who heard about it through a Facebook group.
Dimensions:
Tie bit: Length: 41mm; Width: a hair over 15 mm; Depth: 6mm
Harley bit: Length: 33.5mm; Width: 30mm; Depth with fins: 13.5mm; Depth w/o fins: 8mm
Hex size: Width(flat sides): 2.5mm; Depth: 1.5mm
Complete T-bit length: 49mm
This is how the Harley bit looks off the sprue. It has these little bits on the sides which we will need to cut off to make it look right...
You'll notice that the fins at the bottom edge of the Harley bit are rather tall (5mm). I think for the movie, they were probably trimmed down as I can totally see how they'd get caught on stuff or just snap off. Also, from a molding/casting perspective, those would be a pain to reproduce quickly so trimming them down would make sense to begin with.
Fun fact about the Tie bit: it's not universal. There's a left and a right piece that are mirrored/reversed. I did check the Blu-ray image and found the correct one, which is shown in the photos here. I sincerely hope they didn't mess with us and use the other side for the other bicep piece, and given the time crunch that's usual on a movie set, I doubt that would've been practical.
You can see the depth of the parts when put together. And how the Harley bit isn't raised or shimmed, but it's the correct height. You can also see just how tall those fins are. Also, you can see how the edge of the Harley bit is curved, not stepped. Just a nice gradual curve from the side to the top, no step into a 90 degree corner at all, anywhere on the piece.