LD340 vs LD4B Differences?

I put an LD4B on the 360 I built for my 1976 dodge van that I towed with. I had a smallish cam, J or X heads, headers, and a 650 Holley and ran great. But knowing what I know today it would be an LD340.

1F01C0DA-7F83-4133-8638-E62848F39D5A.jpeg