What are the 3 rear arch types?

[4sfed5]

ok so there is the stradale arch and the group 4 arch...but what the other(s). the listerbell arches look much more bulbous and rounded than normal Gp 4 arches or it just me???

[tipo158]

I believe there are two different styles of Group 4 flares.

[ChrisCar6]

Stradale, the original rounded Group4 round arch, which was a specific centre tub and rear clam, superseded by the rivet-on square arches which converted Stradale bodywork to group 4.

[Fingers]

Stradale, front and rear view.

[Fingers]

Square, front and rear.

[Fingers]

Round, front and rear.

[Bigdry]

But why are there 2 different types of group 4 rear arch? Is there a benefit from one or the other?