100 year old bathroom-suspect bathroom drain was modified late with pvc. p trap is as title indicates. P trap is actually a U trap with 1-3/4 90 degree as long part of P. 1-3/4 ID from wall treaded. 1-1/2 treaded to sink. Not made anymore. No 1-3/4 to 1-1/2 ID reducer available. Tear apart wall or update whole bathroom?