Re-routed the fuel line, but still having warm start problems

I suspect you're having a bit of fuel perculation causing a flooded condition on a hot start. I've never seen a slant 6 have a vapor lock problem since the fuel is on the opposite side of the engine bay from the exhaust. Make sure the heat riser isn't stuck. If it's ok, try adding a spacer under the carb to help insulate it from manifold heat. A stack of gaskets will work if you can't find a spacer but be carefull bolting the carb down so you don't overtighten and bend/break the carb mounting ears. The plastic (phenolic?) spacers work the best. You can tell if it's flooded by holding the throttle all the way to the floor while cranking the engine during one of it's problem times and see if it starts then. A high degree thermostat (195 or higher) will add to the heat problem too so I recommend nothing higher than a 180.