longbow -3", recurve -4", right? but I don't think its carved in stone, most times your guy would probably be right. I'd take the string and bow back to the local shop, he should know what to do when you show it to him.
I did a little looking around after posting
http://www.archeryarchives.com/ if you follow the Ben Pearson links, I stopped looking with the first one I found.
1971, 52", PB-H52, 40-55#s, 7 1/2 to 8 1/4 inch brace height.
no string length listed but I'm thinkn you might want to go longer