With that kind of money to spend, you could get a rebuilt 289 and drop it in.

If you have never done this before, here are some things you will need.(I'd recommend a parts car, because there's lots of stuff needed): V-8 motor mounts,V-8 frame mounts,associated V-8 wiring,5 lug spindles/brakes, 8 cyl. rear differential unit, V-8 driveshaft,accelerator pedal assembly,associated springs,hardware. The swap is easy when you have all the correct parts.