Delta was a company like Cragar or Milodon or Donavan that made parts. They were as good as the rest. If you dig you will find that a lot of the early drives had the front cover mounted idler. As boost went up with overdrive ratios, the block mounted idlers came about. No reason not to use the parts that I'm aware of. In the early 60's, there were many companies mostly based in Socal that made similar parts.
I don't think Delta drives were really a big deal. I do think they were among the earliest if not THE earliest top mounted GMC blower drives. They were sorta simplistic using a sheave and bushing type pulley and a simple drive shaft. Like wfo guy said, I think higher rpms, more overdrive and more boost drove the development of a more sophisticated and stronger drive system. Being some of the earliest of the specialty speed equipment and the relatively small numbers made and surviving today naturally drives up the interest and the price. That's a nice collection of rare old race parts you have there. That old Delta front cover looks a lot like the Keith Black 392 front cover I have hanging on my wall. If Keith used the Delta design he must have seen something good there.
The Jalopy Journal
