If the vehicle was ever stock with a 350 ( or a sibling ) the sweetest way is to buy one with the 350 in, and then you have everything you need.

I once put a 302 into a 68 falcon, which was straight six stock.. the donor engine came from a 68 galaxie, complete with engine mounts, trans brackets, etc. The swap was very easy.

I bought the galaxie for the motor, and after I finished the swap, I sold the galaxie body to recoup some of the co$t.