I just removed the pistons w/ connectings rod only to find out that the crankshaft is ruined or needs serious maching. There is a deep worn groove on one of the journals. This is a 305 engine so I'm reading it is better to just toss this and get a 350? Would a used crankshaft be a good option? Any opinions/advice? My original plan was to use the 305 and do a simple build up, but then I found the damage.

 

Talk to your local engine shop. Show them the crank. If you can trust them they'll steer you in the right direction. Besides, most engine shops have cranks and blocks just laying around.