I just put a set of these on, completely different flexibility/elasticity than the originals. And by completely different i mean the repro'd ones are junk they can be made to work though, heating doesn't help they will melt before getting flexible. It's a completely different material than the original. The reproes are tough sort of chalky texture. What I did was take a drill bit slightly bigger than the holes and by hand turn them into the engine block, the black plastic holes are a separate molded part from the engine so drilling them can easily separate them from the block(from the underside you can see the are just heated and creased with something on the bottom to make them stick to the engine block). If you do accidentally separate one from the block you could probably just super glue it back.
Anyway by hand use a drill bit one size larger than the holes for the plugs, the large hole will take about two drill bit sizes larger, then carefully push with one hand on the top side. I then with my other hand taking care not to crack the block grabbed what I could of the orange repro wires with a leatherman tool pulled from the bottom while pushing the too down. It takes quite a bit of force but after you've drilled(by hand I wouldn't suggest a power drill it would likely demolish your engine) you can get the new wires to make it into their spots.
I would say this project is not for the faint of heart as the corvette engine blocks are as far as I know still unobtainium so breaking the one you've got would be a major bummer.