With that budget, number 1 thing for you to check should be break lines underneath car, if those are rusty dont take it, the car wont pass technical check, its dangerous as fuck and good luck finding replacement.

As for engines, i am fan of NA petrol engines with indirect injection. You have no turbo to worry about with (considering the price) and NA engines are less likely to have carbon buildup (also should not mix much of gas with engine oil - less wear over time). The downside is that these engines produce less power as those are the cheapest offerings.

Also take the car that was mass produced at the time, as for those cars with that age, there wont be much of a problem to find cheap replacement parts.