my first engine rebuild (318) advises

Looks like a replacement rod.

Also, just so you know, frosty is right, the a500 requires modifying the torsion bar/ trans brace area to get it to clear, but it's about the same length as a 727, within 1/2" or so.

If you do go with the a500, you would benefit from getting a higher gear ratio in the rear axle, without hurting your cruising RPM. Shooting for around 2000-2300 is a comfortable range with these engines. Any lower and it starts messing around on you, especially if you live in or near the hills.