We can help, but you will need to get some numbers off of the car. There is no way to identify the correct engine by the vin number. On the top left side of the gas tank its possible that the tank sticker is there. If so, this is the key to all your answers. You will have to drop the tank to get at it so you can read the options that the car came with. If no sticker, then look at the tach redline. 5300 rpm = 327/300hp, 6000 = 327/350hp, 5600 = 427/ 390 or 400hp, 6500 = 427/435 or 430hp. Open up the drivers door and there will be a plate on the A pillar. This will tell you the paint and trim code. It also tells the date the car was made. Get those three codes and let us know and we can decode them for you. Also get the block casting number. This will tell us if it is a corvette block. Three blocks were available in 68. 914678 was a 327. 3916321 and 3935439 both were 427's. Also get the numbers off of the pad. Its located on the passenger side just in front of the head. There will be two numbers. One is the engine code and the other is a partial vin of the car. To see if its the orginal transmission, for a turbo hydra-matic, the production codes are on the passenger side on a vertical plate. If its orginal, the partial vin number will be there. Suggest you get those numbers also and let us know and we'll decode them for you. Also, check the fron sway bar. small blocks had a 3/4 inch bar and big blocks had 15/16. Exception is small blocks with the F41 supension option, but that is rare. Also, if the car has a stock rear sway bar, its almost positive that its a big block car. There are other things, but I've got to limit this for now. Suggest you get those numbers and I can tell you what color trim, paint, etc. the car came with.
Mark
68 coupe