We'll need to hold a séance to talk to someone that marched 'em.
Just kidding... I actually marched tri-toms my first season on marching drums! On the big ol' ancient tubs I had, I think the interval between each drum was pretty close to a major third. The tuning you'll use will depend on what kind/size your drums are. I think the tris I marched were 1970's Ludwigs, 12"-14"-16".
And just for reference, I've got a few years (or more) on most of the guys on these forums, but I'm not that old. When my junior high school started a marching line, we were playing on hand-me-down drums that were older than we were.