Thermo Quad Float

I'd hold out for brass floats.

http://www.carburetor-parts.com/Carter-TQ-Thermoquad-Brass-Float_p_33.html

http://www.carbkitsource.com/carbs/floats/f03.htm

http://www.carburetion.com/Carter4TQ.htm

http://quadrajetparts.com/brass-float-p-937.html