Re: Swap: Marin Ti Stem
I don't believe they made that stem until the 1 1/8th head tubes in 1991. They are made by Litespeed as are the 1 inch Ti frames, so the logical thing to do is buy and 1 inch Litespeed stem, and lose the decals.
The stem above was an optional upgrade in 1991/92. I think your frame is 89/90.
I was faced with the same dilemma on my pre 90 frames. I chose a steel marin stem for the stock spec, and a Syncros upgrade for the race spec one.