Grantham Town have visited Boston 19 times in the Lincs Senior Cup over the years, though the last time was in 2010 when Boston won 4-1. Boston have won 13 of those games. This time it will probably be fairly close but I think Boston should just still edge it to make it to the final against Cleethorpes Town, so I'm going for:
Boston United 2-0 Grantham Town (550)