Try 25-35% over development (~N 1 1/2). Use a well behaved developer that will boost contrast linearly and won't block up, like D-76. Highlight blocking shouldn't be an issue in any case because the subject doesn't have any highlights to speak of. You don't want to use a compensating developer like dilute Rodinal. Pyro is probably a bad choice as well since results can be quite unpredictable without prior experimentation.
T-Max 100 would have been a better choice of film, old-style emulsions don't take nearly as well to developer manipulation.
When printing let the highlights go light grey so they are off the toe of the paper. Bleach them back to white carefully with Farmer's.