What engine can I have?

If you want a V8--> Small block V8 available in that car would have been a 273. A 273/318/340/360 will all be the same physical dimensions with the same outer appearance (give or take a few small things) so you can go with any small block, if you want. A 273 should be cheap, maybe even free, same with a 318. A 340 will cost you big bucks and a 360 a little less than big bucks. You will need a V8 transmission to go with the motor and a V8 centerlink (it's dropped instead of straight across).