My $500 '69 Valiant

Gimme,some input on what y'all think I Should re-build the original 273 probably, expensive parts wise.I have a '68 date coded 340 block which will definitely be expensive to put together,or i have a 318 '72 dated block i could put together. I'm pretty sure that steel crank out of the original 273 motor will work with any block. I know the 340 will probably give me a little more than the 318,but I'm not sure it will be worth it to me as far as cost is concerned.Anybody that has some valid suggestions would sure be appreciated. Thanks Larry.