bikemig 

I like a Campy NR build for the TX 900 since that seems right for a 1978 bike. Of course, BITD people weren't as hung up on going with one group as they are today. Friction means you can pick the parts you like the best and superbe are easily as good as campy NR brakes.

I chose a really eclectic build (post 2 above) mainly because I wanted to use parts on hand and I had in mind a very specific and very hilly ride which ruled out campy for me. That said, I've stripped my TX 900 down and I think I'm going with a mainly campy build. I'll go with a campagnolo super record rear derailleur, a NR front, and simplex super LJ downtube shifters. That will limit the freewheel to a max of 28 teeth. I really like the looks of the stronglight 93 crank and I think I'll run that with 50/37 rings. I like mixing campagnolo with good quality french components to improve climbing gears (the stronglight 93 crank has a 122 bcd), a more durable headset (stronglight A9), and better shifting (simplex super LJ downtube shifters).That will effectively give me a mainly campy racing bike but with decent hill climbing gearing.

I like the OP's idea of going with an older Dura Ace group as well (as opposed to Campagnolo) but personally I'd avoid the 130 bcd crank as the low on that is 39 teeth.

The one suggestion I have for the OP is to figure out the kind of gearing he might need to do his local rides and work backwards from there in deciding which components to use.