How bad do these 3 big mistakes hurt the value of this 340 car?

It looks well done for the price, Detail the grill, new bumpers and tail light chrome call it a day. If you want a correctly restored 340 car you would be redoing the entire car. Stripes, hood scoop are not correct. wheels tires, hood pins, everything under the hood. Its a nice driver.

It may be worth 10K to someone but to a guy that wants a correct 340 car like you or I, Your correct it needs to be totally redone in the paint and detail department.