lightest a-body??

Plymouth Valiant: http://en.wikipedia.org/wiki/Plymouth_Valiant

'61-'62 106.5" wheelbase curb weight 2750#
'63-'66 106" wheelbase curb weight 2692#
'67-'73 108" wheelbase curb weight 2743#
'74-'76 111" wheelbase curb weight 2819 #

Adding 2" to a cars wheelbase makes it heavier not lighter.

Equally equipped, the Gen II W/the shortest wheelbase should be the lightest as evidenced by the above

The "A" Body Dart started out @ 111" so it's not even in the running.

The "A" Body Lancer would be the same as the '61'62 Valiant.

All of the "curb weights" listed above would be for the lightest possible variants.

For the early generations the weights specified would undoubtably be for 170 \6 equiped vehicle W/3-speed manial transmissions.

Later Gen IV cars would have the 198 \6.

Either engine, being 1" shorter than the 225, would be considerably lighter.