Steve40th

Just curious if there is a rule of thumb to ensure catalytic converters, (going to use metal substrate) light off properly. I am using a OBD1 Vette, with O2 sensors at header collectors, but due to my 700R4, cats are tight when right up next to the collectors. So, can they be a few feet back to properly work?
I am trying to keep the fuel smell down to a minimum, as my daughter has asthma, and my 396LT1 isnt running rich, but the unburnt fuel at idle is there, even with heated O2's.