As aluminium alloy is far dearer now than the 70's I'd expect it to use a lesser quality grade than previously, this will have little if any effect on performance but may affect strength, only way performance will suffer is if matching circuit is lower quality than original, which again probably won't affect performance to any noticeable level, its all about profit now, not lastability like original hy gains,avanti's and antenna specialists were all about, much the same as interceptor i10k, might last longer but won't noticeably outperform any other 5/8 wave, would need to use really pish poor materials to do that and even then it still wouldn't be vastly noticeable, just like sirio antennas are barely noticeable from the antennas they cloned but ain't as strong, about the only noticeable difference you'll find of any original antennas compared to todays clones, the one exception may be the original vector 4000 a 5/8 wave over a 1/4 wave colinear,as opposed to avanti's halfwave over 1/4 wave colinear, but was weak as fuck, but sirio have returned to the original avanti 1/2 over 1/4 wave colinear, a small sacrifice on performance to give slightly more strength, I think most antenna companies cloning their earlier or others antennas will do exactly the same, the price of aluminium dictates that, not choice.
Cb'ers want quality at low prices, you can only have one or the other, quality costs so manufacturers have to cut corners to sell at a price they reckon the market will pay, as they still work as well people don't complain until they break easier, price we pay for so many cheapskates in the hobby, can't blame the manufacturers, they are only trying to provide what people will pay for and their source material cost has went through the roof, so they are probably making less profit now than they were when it was financially viable to use the best quality materials,
blame the "incompetant" (really, very competent bankers who acted deliberately) bankers who deliberately put the world in recession so they could buy up property cheap or reclaim it from people no longer able to meet mortgage payments and face repossesion so these shady banking cartels of German ancestry like Rothschild (Red Shield in German) can make a killing reselling them when they decide to end the recession they started, its all about property and profit, nothing else, these people are so greedy they don't care who they hurt in the process of reaping it in, The Royal dynasties of Europe and Oil Dynasties of the States are in it up to their necks too. That's the reality.