By the time one professionally rebuilds a 454, using quality components, fitted nicely (rare) the investment will rival a GM performance crate motor.
A crate motor that's maintained will outlast the truck. A poorly fitted engine will empty your wallet and never be useful.
Either way, there will be major outflows and an idea of actual costs to rebuild cannot be figured until the engine is out and carefully torn down. Mark everyhing for placement. Mic it up and ask a quality machine shop to estimate. My guess is that you'll find out why crate motors are so popular. And don't forget the other parts to complete the long block.. Belts, tensioner, water pump, new hoses, O2 sensors (if you go FI?), under plenum harness, fuel injectors, fuel pressure regulator, filters, fuel flex lines, spark plugs, distributor, plug wires, new heater diverter valves (plastic crap), engine oil cooler lines, motor and transmission mounts...ad infinitum.
Now if you go with a 650 Quadrajet, you can buy a carb and manifold (Holly Warrior Vortec) for less than the cost of the new injectors. 650 Quadrajet is good for 500 plus HP. Easy 500. The carb would be ideal with the manual conversion. If keeping the 4l80 (good idea) the factory FI and electronics are sorta required. Or stand alone TCM will work. The only con to carb is cold start characteristics. This isn't a crises. The fuel mileage is very close with both systems. And the cost and futzing around with programming and reprogramming is avoided.
When shopping for parts, remember to stay with Vortec only. '96 thru '99 BB heads, gaskets, valve train, cam drive, and intakes don't interchange with TBI or older BB 454. Never mix heads or head gaskets.
Now git'rdone!
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