I'd say you might as well go for a 36h. It _will_ be stronger if it's properly built. The weight difference (of four spokes!) will be negligible, and it's not like they're some peculiar boutique size – most decent rims and hubs are available in 36h.
DO get double butted spokes. Don't skimp here – good quality spokes (I prefer Sapims but lots of people on here are DT fans) make a huge difference to wheels and plain gauge spokes will NOT build a stronger wheel. Look at Sapim Force if you're going to abuse the wheel, they're 2.3mm at the elbow, 1.8 through the length and 2.0 at the thread. Excellent spokes.
: P
P.S. drop me an email (pete at ratracecycles dot com) if you want advice or a quote.