I did, I built the car literally from the ground up starting in 77 or whenever the MKIV Cortina was introduced. I borrowed the W/Shop manuals off Dennis Latty @ Latty Ford , Gore. & compared the floorpan info for MK3/MKIV, they are/were both the same, then obtained a MK3 shell & removed all that was not compatible with MKIV from it, around the same time a local Vet rolled his new MKIV which was written off due to excessive panel damage & I got most of what was good of the shell & bought new roof, rear guards etc to make up balance of shell, the guards/flares you mention were made by bringing out the original arch & filling in the gaps etc then pulling a set of molds off that... molds were made in such manner that the LF could be adapted & used on RR & vice versa so I only needed two molds. Doors were made from alloy & I must confess to a minor stuff up in that dept, I did not look closely enough @ the MKIV & ended up with a bit of a 'dip' @ the B pillar rather than the straight thru of the MKIV. made mold for hood/bonnet with scoop & rolled up alloy boot lid. Same Boss 302/trans/diff from my earlier MK2 Cortina was used in this car as well.