Stock piston Rev limit

Well, I've finally begun embarking on the motor project I've had sitting on the back burner for over a year now. And I have a question about stock 318 pistons.

I have a low mile 318 from a 1970 D200, And I plan to build a modest, budget-conscious twin turbo powerplant in the 550hp range. I'm hoping to install a cam kit, blow through carb, intake, 360 heads, and of course the turbos, probly shooting for 8-1/8.5-1 compression on no more than 6 lbs of boost.

To keep the costs down though, and since the block isn't worn to the point to require an overbore, I want to retain as much of the stock bottom end as possible. (save for balancing, studs and arp rod bolts) I know that running boost with cast pistons can be a recipe for disaster, but since this isn't going to be a racecar, I can afford to run it a little fat to keep the pistons cool. My issue though is with RPM.

Most of the chebby guys I hang out with recommend not running stock cast pistons above 5500-6200rpm. (depending on who I ask) The mopar people I know all own 2.2 and 2.5 cars and insist the stock slugs are good up to what the rest of the bottom end is good to. (their stuff breaks alot, btw)

So, asking those with experience, how high can I turn the motor with the cast pistions without them coming apart? Or would the rods give before the pistons do? I really need to know, 'cause my redline will determine my cam choice, head choice, boost, and my final overall power. And I can't seem to find much info on the subject...