As far as what I have read, yes the yellow chromate is corect. But, you can get different effects depending on different variables. I've seen some plated carbs that come out looking like polished gold plating, very bright. That's ok if that what you want but if your looking for a somewhat correct original look, some experimenting will be in order. It would be nice if you could find some old unusable cores to experiment on a few. As far as the cleaning goes, the best way nowadays is an "ultrasonic cleaner" however, beadblasting (being careful of internal passages getiing clogged) is pefectly acceptable. It will remove all of the original finish though. The muriatic 'dip' just prepares the part for the plating. Kinda like a final, thorough wash. The carb needs to be essentially clean before the dip.
My cleaning process; 1 soak in diesel for a day or two (depending on grease)
2 carbcleaner in spray can and small brushes (wear goggles!!)
3 bath in a large electric roasting pan filled with purple cleaner. (about 180 temp)
(electric roaster available at wal-mart)
4 more brushing and rinsing and more soaking if necessary.
5 soak in the "carb bucket " cleaner (from auto parts store-berrymans etc)
6 more carbcleaner in a can
7 Final "hail mary" option: bottle of "The Works" toilet cleaner.
(be forwarned, this is some serious stuff believe it or not and will eat any thing
including the metal itself. good vemtilation and dilution with water.) I dont know whats in it exactly but it eaats through rust like fat boy at a pizza buffet. Hope some of this info helps. ENJOY!!