FYI (and FWIW), LaRocca's runs 50# injectors on several of their ProCharged 302/306s. I spoke to Jimmmy LaRocca a couple times regarding injector size about 9 months ago for my coupe. I too was skeptical of the large injector size, but Jimmy insisted on no less than 42's for my combo - and actually encouraged me to go with 50's. His expertise on ProCharged Mustangs is very extensive. I am no fuel system guru, just lending my observations.
And, again, a properly built 393 w/ adequate cfm from a blower will make some serious HP. I sure wouldn't want to lean out that motor!
E