Create a random value for each gulp-rev-collection replacement

I'm trying to figure out how to generate a unique number for each replacement in a gulp task. I'm using gulp-rev-collector to collect a few manifest files and prepend the relative directory with a cdn url. It would be cool if the prepended output would hit a random cdn cname that we've created. The following works, but it looks like the replacement task only happens in one pass, so essentially one random number is generated for the whole pipe. Any idea how I can get a unique random number per replacement?

var gulp = require('gulp');
var revCollector = require('gulp-rev-collector');
var config  = require('../config').production;

gulp.task('revCollector:production', function () {
    return gulp.src(['public/**/*.json', 'public/**/*.css' ])
        .pipe(revCollector({
            dirReplacements: {
                '/dist/images/': '//nodecdn'+(Math.floor(Math.random() * 4) + 1)+'http://.domain.com/dist/images/'
            }
        }))
        .pipe(gulp.dest('public'));
});