Stroker Build... maybe

A while back... my engine indulged itself in a slight smathering of steel dust. The rocker arm setup was ball and cup. One of the rocker arm balls broke off. The wasn't much dust (.003 .005) that I found, but it was everywhere. Since this happened, I really don't trust the spinning assembly.
The bare block is being hot tanked. While this is happening, I'm thinking about putting a stroker kit in. The existing pieces parts might be okay, but as long as it's torn down. I might as well look into it. Realize that it's been 35 years since I've owned a hot rod. Back in the day, my nick name was Dirty Mike 'cause I was always working on cars. Pretty much all big blocks. Including the big block 318. :) From what I remember 1966 was the last year for it.
That said, I have a few questions regarding the 340 that I have not been able to find the info I'm interested in.
1: How large can the bore be on a 340 without risking issues? My recollection was .060 (for the 440 anyway.. I could be wrong)
2: How long of a stroke can I get away with, without having to do to much metal removal for clearance of the spinning assembly?

The jist of this is, I'd like to end up with a 426CID small block. :D
With a 4.12" bore and a 4" stroke or a 4.07 bore (what it is now) and a 4.1 stroke, either would yield the desired displacement. I have found cranks with both 4 and 4.1 stroke.
The formula that I used is this: "echo "scale=3 ; (3.14 * 2.060 * 2.060 * 4)*8" | bc -l" This was done on a Linux box where bc is a basic calculator. I adjusted the bore and stroke as necessary.

If it can't be done safely, not a big deal. :D
Thanks!