The long type arches are known as flared wings, Note the brackets that support them at the front are identical to the normal headlamp bracket, with the exception of the monger wing support. It’s possible to convert, simply by cutting off the longer wing supporting section, to just leave the headlamp bracket.
As others have said, they cyclewings have different support brackets depending on whether you have Westfield’s own aluminium front uprights or cast iron Cortina type. If you’re not sure, then posting a photo up of the uprights, from the inside, showing the steering arm, will let members identify them for you, (Note, there’s also a third, much rarer option, Westfield fabricated steel uprights!)
Before starting to spend too much though, have a plan for how you’re going to deal with the cosmetic damage once the flared arches are removed, also, do you have full interior trim? As if the arches have been fixed on following the original build manual, you will need to remove the outer interior trim panels to get at the mounting bolts.
As for the cosmetic damage, it’s not just the diagonal line of bolt holes up either side of the outside of the tub, but you can also find that depending on how much the car has been used, there can be quite a mark scuffed into the gel coat where the flared arches have rubbed over time. Plus GRP is quite an odd material, it moves and settles in day to day use, especially with heat and strong sunlight, so it’s not unusual to find that once you unbolt two large panels, that the panel behind, in this case the tub, is no longer flat, but that the spots where the bolts were are now raised as the panel has distorted over time, to match the wing.
If you’re going to get the car painted or wrapped, then obviously this can be dealt with easily enough by filler and sanding. replacement tub sides like the carbon fibre ones from a couple of suppliers will get rid of the fist four or so holes, but not the ones from around the windscreen area back. So you’d still need to do something with those. Worst case would be slapping stickers on!