I hate to be a naysayer but I don't think $500 is going to get it done. If it goes to a shop it will cost waaay more than that but will probably be done correctly. If you can find someone to do the entire swap in your driveway for $500 I would be very nervous about the quality of the work. If your car has a SBC in it now I would estimate at least 20 hours to do the swap. These things will need to be addressed after the engine is bolted in:
-Fuel system (pump, lines, filter)
-Intake ducting (MAF, air cleaner, cold air piping?
-Cooling system (creative radiator hose combinations, heater hoses, heater valve, possible radiator upgrade, electric fan)
-Exhaust system (O2 sensor bungs, original manifolds or LT1s? headers?)
-Transmission (crossmember, cooler plumbing, shifter mods, driveline shortening)
-Electrical (Modified factory harness or aftermarket stand-alone? Wiring to the fuel pump, gauges, fan. How "factory appearing" do you want it?
-ECM reprogramming (delete VATS, air pump, after cat O2s, shift points.
-AC (custom hoses, wiring, recharge)
-PS (custom hoses, mount reservoir)
Kinda looks like the 400 was the easy way out :lol: . If you have the tools, skills and location I would suggest doing it yourself. The LT1 is a more direct swap than an LS but don't expect to just drop it in , connect a fuel line and a power wire and be on the road. I'm certainly not saying don't do it -- just be aware of what it really takes to finish the job.