I have a tr3550 which seems to have a similar bolt pattern except for two bolts which are narrower than the rest whereas the tko shifter is a rectangular shape. Jump to latest follow.

How To Improve The Shifting Of Your Tremec Tko Transmission
Tremec tko 500 problems. It turns out that tko 500600 has a significant design flaw that tremec knows about and chooses not to fix for ease of production and cost reasons. Fits tremec tko 500 600 5 speed aftermarket transmissions. Got a good deal on a pro 50 shifter for a tko 500. The tko 500600 uses a total of nine pads for a complete transmission. This is the 1 2 fork with three pads while the fifth gear fork uses only two. According to the build tag was a sept 17 build date.
Walsh says some early tkos used two pads on the. I ended up going with the 5009 because i liked the 64 od and higher torque rating gave me some margin for safety with slicks. Does not fit tr3550 or any other model see separate listings. If the input shaft on a tremec tko has the slightest drag or misalignment in it and spins in neutral you are going to have that grief. Problems with tko 500. The flaw affects third gear.
The tko input shaft seems to need perfect alignment and perfect fit to the pilot bearing center any misalignment will cause the input shaft to rotate casing grief in shifting. Or 07 i guess but i doubt that i was concerned about getting an old stock item but it was reasonably new.