Not sure if this is too late, but here's a suggestion
Boston,MA to Albany,NY - your preference but I prefer Rte 20 west of Worcester.
Albany,NY to Seneca Falls,NY - basically stay on Rte 20.
At Seneca Falls you can pick up ACA Northern Tier and follow it to Oberlin, OH.
At Oberlin,OH you can pick up ACA Underground Railroad and follow it to Maysville, KY.
From Maysville,KY to Bardstown KY, you're on your own, but there aren't a lot of options so I doubt if you'll get lost.
At Bardstown KY, you can pick up ACA TA route to Pueblo,CO.
Not all of this will be pleasant but it is a fairly direct diagonal, taking advantage of intersecting ACA routes.
Have fun and try not to focus on speed (unless you MUST)