Looking at the yellow one, there is a staggering amount of modifications required to produce that shape, for instance it looks like the "fins" on the rear wings are taller at the ends. Next, it looks like most of the top moulding that runs from the bonnet to the boot lid has been lost. Then there's the roof, looks like a chop and greater rake on the front and rear screens, no front quarter lights, you'd probably need a full set of custom glass, also looks like the roof has been narrowed to give more slope to the side windows.
I'm not saying it's impossible, nothing is, but you'd need a boat load of time and all the skills of Boyd's crew ! Not to mention another boat load of cash.
For comparison here's a Graber coupe.