I figured I would put my 2 cents worth in on this subject. Look at the facts. You have a hemi; and it is possibly a hemi that belongs to a certain car. The serial numbers have been ground off. This creates some doubt or at least suspicion. The other party does not want to give up the car. Now, think about this. If you partner with this individual, will that car ever be restored to factory original? When it is finished, would you sell it to make the money? Chances are it won't sell as original since the numbers have been ground off, and any serious investor looking for one will certainly question the validity of the VIN number on the block and shy away because of this debacle. Who will you have to restore the car? If the other party hasn't already, chances are it won't be restored. Everyone knows it is bad business to partner with someone else especially on one common project like this. Who will have possession? Who will have registration? Possession is 9/10ths of the law. I don't think this other party would let the car out of his sight. Are you willing to risk your hemi for that? This is a lawsuit waiting to happen. In conclusion, I would sell the motor to the guy with the car for the amount to buy yourself a complete 528 Mopar Performance hemi, or comparable from Dick Landy, as compensation for this guy to have maybe the correct hemi for his car. The new blocks are stronger, and it is still a hemi. It has more horsepower, and you will not have to scrounge for original parts. Otherwise you have a hemi with grind marks on the pad. I am sorry but that would send up serious flags if I was looking to get work done on it. It may raise questions to the machine shop also. If they are reputable, they may contact the authorities to see if it was stolen, and that could lead to a lot of hassle. Way more than you want to be involved with. Sorry to go on, but look at the big picture so you don't get burned down the road. I am waiting to see how it goes for you though.