There is no question that you need the entire fastback interior structure... the upper frame above the door is curved on the fastback, so you can't use any portion of the coupe's roof structure other than the top of the windshield frame. Without the donor structure there is no place to mount the roof skin, top portion of the quarterpanel, the rear portion of the roof panel, panels to mount the trunk hinges, trap door etc... Almost everything in the auction is welded directly to the sub structure.
He would be much better off just saying that this is a STARTER Kit, and not be stating that this kit is "everything you need" ... that's just plain outright lying!
I am currently doing one of these conversions, and I've gotten every piece he lists in that auction, (thankfully not from him) and there is no way these pieces could be used without interior support. My original intent was to just use a complete donor top half, but the panels, just weren't worth the effort, so I sprung for all these repro pieces. There's no question that the dynacorn pieces are well made, but again, there's no way you could do this without a donor structure or some very serious fab work...
Regarding asking questions before making a large purchase like that on eBay, I agree, but that's still no reason for a seller to lie in the description.
Here's my donor structure pretty much skinned. This is not something I'd want to build from scratch...
'68 Highland Green, custom built tubular chassis, Fox rack & pinion steering,'89 HO/331, Cobra intake, E303, AFR 165 heads / T5z spec transmission,
8.8" rear end w/ 3.27, Auburn limited slip, triangulated 4 link, QA1 coil overs front and rear, Cobra 4 wheel Disk brakes. '01 Silver Bullit wheels.
Was a coupe, now with a fastback roof. First run 13.3 @ 107.