I'll second the suggestion to use Phil Wood hubs and also suggest using the Sun CR rims which come in 27" or 700c, are very sturdy, and run $30-40 a piece.
A bullet proof freewheel for 126 spacing and heavy riders would be a 7 speed Sachs Aris. The notched teeth improve shifting and the bearing cages double as seals, keeping contaminants on the outside. The only caution is that the original grease in a Sachs Aris usually degrades into a sticky peanut butter consistency and needs to be cleaned and replaced with a modern synthetic. Finally, the less than adequate freewheel servicing method I refer to as "flush and dribble" can't be used on Sachs Aris due to these seals.
The notorious contaminated "Peanut Butter" grease in a Sachs Aris prior to cleaning.
