I haven't built a Cleveland in years, but that doesn't mean I don't know what I'm talking about! My 480hp (400 crank hp) 393W was built for under $3k, albeit using used heads... Would I want it to run at peak power level for a 500-mile race - no. But for the normal street driving (plus the dozen times a year I take my car to the dragstrip) it is doing just fine - for the last four years!
OK, back to the topic --
OK, if you want a forged 383C or 408C kit, (forged crank, H-beam rods, forged pistons, rings, bearings, and balancing), that is ~$2k. The cast kit I linked earlier would be fine for a street motor. Do the headwork to install the bigger 70-72 valves into the '73 4V heads for ~$800 (including valves) Figure another $400 for block prep. Add new timing set, oil pump, pump drive... $200. Retrofit roller cam kit $700. Pushrods - $100 Gasket set - $100. Intake manifold (Edelbrock Performer RPM air gap) - $300. Roller rockers (Harland Sharp) - $250, New water pump (just because) and rebuilt Duraspark distributor -- $120.
Total - $4970
Of course, the cast rotating kit I linked to earlier would be about $600 cheaper, so that's a total of $4270. That includes things (like the intake manifold, water pump, distributor) that drove the cost to over $4k...
Or get a pair of Trick Flow aluminum heads for $2k and forget the machining to the cast iron 4V heads - $2k for the Trick flows minus the machining to the stock heads, so that's an additional $1300. Total cost now $6270
OK, so what do YOU see wrong with my thinking??? According to my computer software predictions (both DD2000 and Comp Cams CamQuest6), with the components I specified above, ANY of those kits will produce over 500 crank horsepower, and most would be knocking on or even a bit above the 600hp threshold!