AllI got from My dad was a 20 ga Ranger.
I wouldn`t worry abt. the bores on any of them. A cousin of my wifes had a 722 Rem. in .222 that he bought in 1960 and in 1999 told me it didn`t shoot good any more. He carried this gun in his pick-up all those years and it was well worn. I briught it home and run 50 patches of Sweets 7.62 through the barrel and the last patch was as blue as the first. Getting tired of this I took it out and shot it, 1/2 in. at 100 yrds. I put some finish on the stock and took it back to him, figure I`ll clean out the rest of the copper in another 20 yeasr when he brings it back to me.
I would recomand you forget the new stock for the .243. If you must, fix it up as best you can, but above all take it back out in the wood and hunt with it.