The difference between the 305 and the 350 is the bore dia. The 350 is 4.00"
and I believe the 305 is 3.75". The 305 can't be bored nearly that much.
They do make stroker cranks for the 305 that will increase your displacement
somewhat, but 350's are so cheap and plentiful it's really a waste to
consider anything else.
The wrecking yards are full of them. How much did you want to spend? You can
buy a brand new 350 long block for under $1500.
for $1700 you can get more of a "Hotrod" motor brand new.
The 350 Chevy is probably the most plentifull V-8 out there. You should be
able to find a good used motor for a few hundred bucks. Keep looking. You'll
find what you're looking for
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