To date I've tested just about every "upgrade" for the stock HEI module. Even one with rev-limiting dip switches on it.
Some worked fine, others did not. Without exception, sooner or later every single aftermarket module bit the dust and I had to go back to my 990 module.
On the dyno my "stock" HEI with 990 module made just a tad more power in a back to back test than an MSD billet distributor with a 6AL box!......