I'm considering buying a 1975 280z with 150K on original engine. Great condition. My question for the long-term is if I ever needed to buy a rebuilt engine, what ballpark price am I looking at? Thanks!

$1800 to $2200 is ball park in my experience (CA prices) with a 240Z motor rebuild. Except for the EFI there isn't much difference between the engines in terms of rebuilding.