I've got a Centurion Comp TA from 1984, and am getting it sandblasted and repainted soon. The downtube shifter braze-ons are different than I've seen on any other bike, having a "stop" built into them rather than being part of the curved-spacer piece that sits between the frame and the shifter.
I think this precludes the use of indexed down-tube shift levers with this frame, because the right (rear) indexed shift lever requires a spacer that can't fit over the braze-on of the TA Comp. The bike came with Shimano 600 components including pure-friction (no racheting) down-tube shift levers, that worked perfectly well with the brazed-on shifter mounts on the frame.
I'm guessing that I can't use indexed down-tube shifters with the braze-on mounts on the TA Comp. No biggie - I'd probably have planned to use bar-end shifters even if the down-tube mounts were normal. But it's nice to know one's options.
1) a normal down-tube shifter braze-on, without the curved spacer.
2) normal braze-on with the curved spacer from Shimano indexed down-tube shifters
3, 4) TA Comp braze-on
5) TA Comp braze-on with aluminum spacer press-fit over the braze-on.