Oregon 76 is sadly discontinued. There isn't really any direct replacement. It is a regular 3/8 pitch (not LP) chain, with full sized drivers and tie straps. The cutters are lower profile than regular 3/8 pitch, but not as small as LP cutters. Closer to .325 pitch cutters in height (and a 3/16" file is the correct file for them, as it is with most .325 pitch chain). I like Oregon 76 on 40-50cc class saws for which there isn't an easy way to run LP (such as my Homelite Super E-Z AOW). There was both regular and 'safety' versions of 76. The 'safety' version has the 'shark fins' that we see on many other Oregon consumer/safety chains. There are loops of 76 (both regular and safety) on ebay from time to time if you want to just get another loop of it for your saw.
Banana bars were indeed OEM on many Echos (and Poulans). I've seen NOS Echo branded Oregon laminate and 3 rivet replaceable tip bars wearing the 'guard tip' (which was the 'banana' version of their 3 rivet replaceable tip). Your 3400 and 452 both come from the era where those two manufacturers were installing 'banana' bars (and both saws use the same mount).
Oregon 76 was a good match for your 452. It can run 3/8 pitch chain, but would probably be happier with .325 pitch come chain replacement time. That would of course require a sprocket and bar change at the same time. If you don't get too aggressive with the raker hight, it'll be fine with Oregon 72LGX or 72LPX. Don't think you need to go with skip on a 16" bar with that saw. The 3400 will run a 16" bar with 72LGX or 72LPX without breaking a sweat.