If I'm not mistaken those L2292F's are no longer available. Unless they recently tooled up again. Think it's been since 01-02 since they went away. Also with those and 74cc heads your looking at 11.6:1 comp.

Check Probe pistons. They sell a nice forged 390 flatty and a dish that won't break the bank. And they are nice and light!!! I see guys like Alex and Mad Dog on ebay every so often with really good prices on these. Diamond also makes a nice off the shelf 390 slug but costs and weighs a little more. Keep in mind stroking will not give you a higher comp ratio. It will give you more torque though. The piston, head and gasket combo will deterime that. There is also quench and static compression to be factored with your choices. Just to clear that.