As far as I know, servos won't make you stop you any quicker anyway. I think they just make it easier to push the pedal down, a bit like how power steering helps you to turn a steering wheel. If anything, I reckon the biggest benefit would be ABS, if you went for a big engine. I was on the motorway the other day, driving like an idiot in the fast lane again, thinking 'if everyone slammed their brakes on now, I'd be the one who locks up and slides'.
Asides from the beam not having the mounting point, is retro fitting a servo a problem to a bus? One can always get a beam with the mounting points I guess.
No problem. I'm just about to do mine. I got a servo/master cylinder/reservoir/actuator rod for £44 delivered. Someone on EB is posting me a bracket chopped from an old beam. Attach above assembley to the brake pedal and bracket and tack the bracket to the beam. Remove, weld properly and refix. Add servo pipe and one way valve to the inlet manifold and job done. If you're lucky you might have a replacement beam on your bus that already has the servo bracket, though if you're RHD you'll probably find your beam came from US and the bracket's on the wrong side. I wouldn't advise trying to move it as you'll damage your beam or the bracket. I'll do a how-to when I do the job. Last one I did was PMACS bus and it took less than a day all in.
ABS is for girls. If you find yourself locking up in your bus then just pump the brake pedal like crazy and hope for the best. If you do have to hit the vehicle or tree in front of you then just remember to swing your legs out from under the steering wheel at the very last minute.