On campus, the Vet Med college is now located east of Jack Trice Stadium, it used to be at the intersection of Stange and Pammel Dr. It was relocated in 1976(?). Just south of Jack Trice is Reiman Botantical Gardens opened in 1995. The Memorial Union has a south entrance that is very nice and the inside of the union has been remodeled. Since 1970, the part of campus that has changed the most is the west side. From the north side of Friley north along Bissell Road are 6 to 8 new buildings, mainly engineering. Pammel Court Quonset huts no longer exist and have been replaced by apartment style housing on one side of Stange (east) and non-academic buildings on the other side (west). Just west of Central Campus is the West Quad located between Beardshear and Marston with the north end of the quad being Parks Library (large addition made in 1983) and the south end being 'Alumni Hall'. It used to have a couple Quonset huts and a parking lot for the library. Now it is a very nice green quad. In addition to the above lots of other changes have happened. You for sure should drive around campus but there is road construction on Morrill Road between the Library and Lebaron - which is being demolished - so to access central campus you will need to take Union Drive from the north side of the Union and drive north.
Off Campus, if you take University (formerly Elwood Drive) south under US 30, to the left (east) is the ISU Research Park and to the right (west) will be a 'new' residential area ('new' since 1970). South Duff has been heavily commercialized. Downtown Ames is a very nice historic downtown area. Going further north on Duff, Mary Greeley has expanded many times since 1970. Continuing north on Duff will take you to Duff and Grand intersection. From that intersection, to the left (south) is North Grand Mall constructed in 1971, and to the north is a Wal Mart and another small retail area. If you turn north on Grand and drive down the hill on the left (west) will be Ada Hayden Heritage Park. It is Ames best municipal park in my opinion. It used to be Hallet's Quarry back in the 1970's. It is a 437 acre park with two gravel pits turned lakes. The beginning of November you might see migrating ducks and geese on the lake. The last thing I will mention is that on the far east side of Ames between Dayton Road and Interstate 35 many large businesses and mfg facilities have been built.
Oh I forgot, Mortensen Road that used to be a gravel road that went from University (Elwood) west to South Dakota has had lots of development along it. And so has Stange Road going north from campus. Both are worth a short drive to see all the changes since 1970.
Enjoy you return trip to Ames.