Possibly not without messing with the H. Pos and V.Pos pots, which you'll most likely do anyway. Depends on what MAME settings you have and the game. If you have -keepaspect active, it should fill the screen with a 4:3 image, but this isn't always the case as some games deliberatly output these boarders AFAIA, some don't. You may see some changes, might not.
On a quest for Digital 573 and Dancing Stage EuroMix 2
By gods I've found it!