If you have the original engine in it,you're not going to be going fast enough to need more brakes. Does your truck have a hydrovac on it. If not, that will do wonders for braking. I have a 2 ton and a 2 1/5 ton GMC with hydrovac and they have all the stopping power I feel like I need. If you want to get the truck ready so you can use it within a reasonable time, I wouldn't attempt any of the modifications that require narrowing the steering axle. It's doable, but its a lot of work that I think is unnecessary for a truck that you want to actually use but yet have the novelty of driving a 60 year old truck.
454 big block, potentially supercharged later on powered by either a TH400 (which I already have) or a late model Allison.
So yes... it will be able to do 65+. With the power this 454 is capable of; 100+ is not a challenge. Granted I will limit the truck to 70mph via governor.