I have had a TKO 500 and 2 TKO 600 .82s in my 427R SPF. My experience is that a shifter will not fix a TKO. I am using a Pro5 with a Jordan arm and I think it is as good as it's going to get...which isn't great. The 2/3 shift at 6000+ rpm is not reliable in my car. I have just bought a new, modified 600 from these folks:
WELCOME TO LIBERTYS HIGH PERFORMANCE. The car is in Dennis Olthoff's shop for some major work and will have the new transmission installed when I get it back in about a month. I will post my impressions after I have put a few miles on it. I am guardedly hopeful.