is the engine mount numbers on the front side or back side? I gotta believe its going to be tough to see them with the headers. It does have a big block heater core, had a factory big radiator in it, pretty sure the big blocks sit slightly to the passenger side also.
Its for sure a orig RS also, back in 88 I bought GM brand new quarters, fenders and a rear tail piece and the holes and wirings were all factory for the reverse lights, came with all the vacuum tanks and actuators still mounted, but had to change the actuators to operate the doors. Everything worked perfect for a couple years after the restoration until the cheap aftermarket color coded vacuum lines started cracking and leaking haha
The deluxe interior is all original and perfect except for the headliner and rear speaker deck. the headliner was only changed because a smoker in the rear seat decided to poke there cigarette threw the head lineer
The carpet still has a tag stapled on it but its not a GM name on it, been a while since I looked at it but its dated 1967 and the car is a January build so I know its factory
