The last forks are the 1996/7 version of the Rockshox MAG21. With a loped of brace one the top cap not screwed on ;-)
They'll be 43mm* and fit perfectly on a 1992 Marin as that's when the MAG series were initially released, designed not to alter the bike too much and didn't really change much other than stiffer and better internals since 1992.
The other are modern 2006ish forks, probably work really well and came in 60 100 and another longer still length, you could look up to see how or if you can alter the travel if you wanted to try different lengths.
Unless when you put air in them and they extend a lot more.
*unless you