I have just done this mod after many fruitless attempts to salvage the stock BS38s on my '77, (after resoldering floats, new o-rings, new diaphrams, jets etc, turned out PO had overscrewed mix screw INTO the carb body!)... Got a pair of 2001 EX500 carbs off ebay for 50quid, cleaned em, rejetted (138, 38) and new 34mm manifolds, RamAir filters and....
off we went! Runs beautifully, no popping on deceleration, good pull all the way through, (though not had a chance to open up and strectch legs much over 50 yet, I live in London!), and sounds much nicer, really barks when blip throttle!
only problem was throttle cable. I used the stock one, which was plenty long enough, but didnt pay enough attention to adjusting correct length, meaning there was too much slack meaning when throttle rolled full closed, it was bending the exposed end at carb, and guess what? SNAP! lesson learned anyway, new cable on its way, to be correctly adjusted...
otherwise, bloody great!
oh yeah, so Ramair pods and straight through pipes, stock ignition.