After using the search feature aboard this site, and google (I do not trust myself with a tape-measure [Measure twice - cuss once] ), I have come up with what I think might be accurate...

Swingers and Scamps are built on the 111" platform, while Dusters, Dart Sports, and Demons are on the 108", and older valiants are on a 106" platform.

Would anybody be willing to confirm this, before I spring for the incorrect length frame connectors?

'60-'62 Valiant, Lancer: 106½"
'63-'66 Valiant, '63-'66 Dart wagon, '64-'66 Barracuda: 106"
'63-'76 Dart, including Swinger, except wagon, Demon, & Sport: 111"
'71-'72 Demon, '73-'76 Dart Sport: 108"
'67-'73 Valiant, except Scamp: 108"
'71-'76 Scamp: 111"
'70-'76 Duster: 108"

This is for most models around the world; there were some 111"wb "Valiant"-badged '63 to '66-type A-bodies in Canada and South America.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan!