Another, more Eroica friendly option might be to swap out your Sugino Mighty cranks for a Sugino Mighty Tour. (If your cranks are Sugino, they're almost certainly 144mm BCD, not 130mm. Shimano (Takagi) were the only ones using 130mm in this era.) They're period correct, and with a 110 BCD, would allow you to run as small as a 34T inner.

Here's my Miki built 1976 Centurion Semi Pro sporting a Sugino Mighty Tour before Eroica;

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