Table schema:
CREATE TABLE table_name_43 (slope_length VARCHAR, name_or_route VARCHAR, construction_year_s_ VARCHAR, type VARCHAR, elevation_groundstation VARCHAR)

Question: Which slope length has a type of surface lift, and an elevation groundstation smaller than 1974, and a construction year(s) of 1971, and a Name or route of alpmatten 1?
SQL: SELECT slope_length FROM table_name_43 WHERE type = "surface lift" AND elevation_groundstation < 1974 AND construction_year_s_ = "1971" AND name_or_route = "alpmatten 1"