Helped two friends with two 389's, both .030" over '65 engines. Both guys ordered Ross pistons with a dish of about 13cc's. Price was about $550 and this was 8 or more years ago. Both engines scream on 89 octane fuel.
I think the shipped price for Ross dish pistons, plus pins, plus shipping is over $800.
Auto Tec pistons will be closer to $600, or a bit less. Also, the Auto Tec pistons are made of 4032 material, which expands less. The Ross pitons are made of 2618 material, which is used in racing pistons, & expands more when heated.Many agree that the 4032 material is better for street engines. 4032 pistons require less piston to cyl wall clearance.
I think I've mentioned that if you want Auto Tec Customs there are some Pontiac engine builders who can order 'em for you. When I called Auto Tec, they told me to contact Shannons Engineering. Apparently he's a high volume dealer for Auto Tec. He quoted me a price of about $450, plus shipping, for some Pontiac 350 pistons. That was maybe 3 or 4 years ago, now. They have gone up a little since then. But, I'm guessing that $500-$550 plus shipping, should buy the pistons & pins.
Next cheapest piston choice appears to me to be the 4.120 Icon pistons I mentioned, then grind off the sharp edges of the valve reliefs, to reduce compression a bit.
Cheaper than that is the Speed Pro L2262F 4.120 bore pistons, then remove enuff material in the valve relief area to reduce the CR.
Did a little digging in the DSS piston cat. THEY OFFER A 389 PISTON WITH A 14cc DISH.
The part number looks to be 6105X. Their 389 pistons come in 4.080, 4.100, & 4.120 bore sizes. Don't know what their direct price is. Summit sells their 2-relief pistons for $570 shipped, but don't stock any. So, I assume they could order any DSS pistons & have 'em shipped direct from DSS.
I called DSS. They do not stock any of those pistons. But, they can be ordered thru Summit & shipped direct, after they make up a set.