Add a layer to the can of worms with Canadian spec cars where GM's "predictable engine colours" seldom matched what was going on in the USA.
(and pre-70s Canadian Pontiacs often had Chevy engines in them).
Bedazzle your car, cover it in Z/28 decals, whatever. If you chip off some resale value that is your choice.
It's those trying to pass off something as an original Z/28, GTO and such that is the problem, not the cloning.
I love late 60s Pontiacs. Unless it was a stellar original example I would very likely swap a GTO enduro nose onto a 68-72 onto a Tempest or LeMans. Me, personally I would put the LeMans script in the spot GTO is supposed to go in the grill opening as that amuses me. But I wouldn't put Cobra decals on a Mustang. Not sure what that says about me.
If someone always wanted a GTO and their way of getting it was a clone, thumbs up to them. Ditto for the replica cobra crowd and so on. Live the best version of your dream that you can.
Well I can't think of a situation where a NOS block would have your VIN stamped on it. Lots of frames have the VIN or part VIN stamped on them too. Stamping a frame would be frowned upon by some for sure.
I would suggest the above is about representation: stamping a number on something could be construed as faking it to deceive.
A NOS grill on the other hand likely has no stampings/labels different than the one your vehicle came with. The only clue you have swapped it might be if the vehicle is in rough worn shape aside from a really, really nice grill.
Original block adding value is really only a thing in the high end muscle cars and such where you can actually prove via factory paperwork that said numbered block really was the factory installed one. Pre 70s it is really hit and miss which vehicles you can actually 100% verify the engine was the correct one. If it isn't something you can prove with paperwork and absoluteness (rather than a date range) I wouldn't pay a dime extra for that story.
So people pay for that pedigree. The fallacy is the auction shows making the public believe # matching engines matter on a beat condition early 60s 4 door sedan --or even my not-special-specifications 69 Mustang Coupe if we are being honest.*
*with allowance for the recent "survivor fad/hype" giving a value boost to original vehicles with provenance.
After 50+ years, how many "babied originals" do you think there are out there, realistically? I think SEVEN - and Wayne Carini and Jay Leno own four of those, so good luck finding and buying one of the remaining three! 😋
I'm fortunate that there are a few mechanics in our area willing and capable of working on carb, points, etc. vehicles.
I'm a great believer in "marrying" my vehicles to a mechanic or at least a shop.
Yeah, because of silly things like that is why I don't show my cars. I can however see the attraction for a owner.
Think it boils down to how our brain reacts to things. Mine gets all tingly as I shift gears, listen to the sounds, smile & wave back to folks & try to drive very safely so my face stays away from that beautiful steering wheel & dash.
A person who does the show route might get turned on by researching the proper parts to use, making sure to apply the correct over-spray, etc. Smiling & talking to the people who admire his/her car.
Both types should be experiencing fun & joy out of the game. If not, they're doing something wrong.
I don't include those that do this for the money, thinking of the profit they might make. They don't get my respect.