340 PISTONS: Between a rock and a hard place

Why do you feel boring your block isn't a good choice? IMO boring it will more than likely straighten out the cylinder walls promoting better ring seal
Mainly because you can't put metal back once you've removed it. Boring a standard block .020 over is the equivalent of about 80K of useful life. But I hear you on the straight bore issue. Really hadn't thought of that.