420A stock internal limits

Has anyone gone past the test 8-10 psi (over 275hp) on the stock internals? Any places I can get good forged pistons and rods for cheap? but not "too" cheap?

You can always go over 8-10psi on stock internals. It's just a matter of how long they'll last. Safe running on the 420a is 4-6psi. Anything above that on the stock isn't going to last forever.

And don't go cheap on internals. Spend the money if you're going to boostin. Do that, or you'll be spending more money on the same thing later down the road.

Its all about tuning. And luck of the dram with your motor to. Some people blow theirs at 8psi, some will run 10psi and the motor will take it for a few months. I have heard of one guy running 15psi. Now I highly recommend you dont try this. The biggest problem is tuning. As long as you dont get knock and your a/f are perfect you can turn the boost up a little more. If you want to run high boost go ahead and build the motor.

Its all about tuning. And luck of the dram with your motor to. Some people blow theirs at 8psi, some will run 10psi and the motor will take it for a few months. I have heard of one guy running 15psi. Now I highly recommend you dont try this. The biggest problem is tuning. As long as you dont get knock and your a/f are perfect you can turn the boost up a little more. If you want to run high boost go ahead and build the motor.

I agree, and you should listen to silver. The only thing I think you failed to mention is that even with perfect tuning, your boost can push the internals beyond the amount of pressure they can handle... resulting in a bent rod.

Forged internals are always nice, even if you don't plan on making your car a supercar, they at least give you extra protection in case you ever knock...

Edit: to answer your second question, you can find deals on e-bay. The pistons and rods can come as a package.... I b/l a/b $750, but don't quote me on that.