Going to be tough on a 5K budget. Not impossible, well, you’re going to have to score some deals to make it happen. A good rotating assembly is going to eat nearly half your budget. Solid roller cam, lifters, springs, pushrods, etc. is going to eat another $1500-2000 depending on what you get. By the time you get a good oil pan, pump, pickup, rockers, intake, balancer...you’re way over budget.
If you have the bottom end from that 454, get rods worked with good bolts, get crank reground by someone that knows their stuff, use those 781 heads, that will save a bunch of money, live just fine under 7000 rpm, and done right will make more power than you’d ever think possible..and there’s a good chance you’ll be under your budget.