Just some thoughts on your wheel options. Since you're a big guy, definitely go for a bombproof build. 36-hole and 14G spokes. Chasing after NOS vintage parts can get very expensive. I can't say I know pricing for NOS 600 EX hubs in Canada, but that seems high. I realize stuff is scarcer and costlier up there. (Lived in MTL)
I'd go the 105 freehub route. Stronger, reliable, smooth, and can handle 7-10 speed set ups. If they are being professionally built, ask about alternative lacing, a 2x NDS/3x DS should yield a more reliable wheel. I like the Velocity offset rim for your purposes. Less dish, more strength for your load requirements.
I think it's safe to lace as you please up front...radial, 2x, 3x, crowsfoot. All will be strong at 36 holed.
Old hubs and rims are some beautiful equipment, but if you're starting from scratch...take advantage of modern wheel options for their advantages.