That 305 can be rebuilt to be a good solid every day motor..they do have a small bore and the small valve heads and sorry the big valve 350 heads don't fit...
But then a port cleanup and decent cam and a solid rebuild can give you an engine that will give a good service for the parts chaser..
350's can be found by keeping your eyes open for cars/trucks that have one..If you find a good seasoned block and heads somewhere..then do that one..Heavens if one keeps their eyes open and ears to the ground and gets out and about one may even find a big block..
Depends on what you want to do..I keep my parts chaser as a good running fairly stock truck for a nice ride and good reliability to go chase parts with..Now my project car is a whole different deal..<<grinn>>
I have tried most all of it and now do what is known to work..