Now, I may be wrong here, but I am willing to bet this car was once a small block/automatic car. First, the fact that the tunnel and pedals are for an automatic kinda back up this point. If the tunnel was replaced or patched, then they did a darn nice job and I cannot see any seams that would indicate a patch put in place. The hole on the tunnel is for an automatic as well. Also, I have been tracking Z11's and Z10's for several years now and have a reasonable list going. One thing I have noticed is that with the Z10's, they are built in lots of small blocks and big blocks, meaning that they did not build just one big block Z10 in the middle of a small block Z10 run and reverse. In my list, I see several 350's being made, and then several 396's being made. If this car were indeed a 396 car, it would be the only big block car made in the middle of a small block z10 production run.
Again, my list is not complete and comprenhensive, but if I go by the info I do have, than this car is either a small block car, or an anomoly.
For the seller to advertise this car as a big block/manual trans car seems to be sketchy to me. He advertises the engine and trans as "date coded" but cannot verify the partial VIN. Without the drivetrain in place, no one can make this claim. Having a date coded engine and trans does not mean the car is originally a big block car with manual transmission. This car may very well have been a small block car with auto transmission. The items that would indicate this car as a big block or a manual transmission car are somehow missing or in contradiciton. The lack of the heater box, the pedals and trans tunnel for an automatic, etc.
Also, according to the info I have, this car should have a black custom (comfortweave) interior, not white as provided with the car.
Again, I may be wrong. I can only go on what limited information I have.