interesting... where is the cutoff for older/newer? I rebuilt a 360 (stock) for a 01 Durango and used a set of EQs assembled, plopped them on out of the box.... went to $#!t with less than 3 hours of total run time.
I put 6 miles on that engine, 3 of those miles were "non running" on the back end of a tow strap. I pushed the Durango back into the garage and "forgot" about it til this last weekend. I picked up a good used low mile 360 and decided to pull my brand new EQs off of the fouled engine, while I regasketed the whole engine before sticking it in there. SURPRISE//// #4 exhaust bent pushrod W T F? pull valve covers... #4 exhaust valve stuck. Pull heads. that valve is bent to He11 and I see the imprint in the head of my brand new piston. Heads are in the machine shop for repair as we speak. I built this engine in Oct/Nov 2016, and Durango has been sitting since then untouched.
How would I know if I got Australian or China heads? This is the 3rd set of EQs I have bought and used, 1st set was bare, 2nd set was assembled, running fine on my son's Ramcharger, this being the 3rd set I have bought. The 1st 2 sets came shipped to my door, the "problem" set I picked up myself and paid for at the AAEQ Midwest warehouse in Chicago. I remember when I was there, they had PILES of these heads brand new in boxes...… I know 110% for sure, the bare heads I bought and put onto my 83 D250 were Austrailian cast. I had 5 cracked OEM heads here that I stripped, and cherry picked the best 2 heads' worth of hardware out of that 5 heads' worth, touched the valves up on a valve grinder, hand lapped then and put them on.