Would depend on other things, like the tranny. If it's a 5-speed, I'd figure in some $$$ to replace it when it goes belly up.

Also consider emissions, if they would need to pass them in your state. An altered system like that may not pass a visual, or a sniffer, depending on how the HEI and holley were installed. Could lead to a big mess for a new buyer, and big $ if they had to put it back to original.

And rebuilds are great, but if the axles and other parts have 170,000 on them, $4K might be high.

Pete