Stig, if you use FT TC4 arm blocks you'd have to upgrade to the TC4 control arms, hinge pins, etc, because the TC4 has larger hinge pin diameters with a ball cup type of setup in the arm mount blocks.
I think aluminum blocks were available but not sure who produced them, if they're still available. I always ran the plastic/nylon mounts with my TC3, if one got whopped out I just replaced them with new ones for $5-6. I replaced the blocks a few times over a couple years and it was much cheaper than buying $12-16 per block for aluminum.