The 01D would indicate 01=January and D=4th week. Your engine is January 6 1970 which would make it very possible that it is the original engine. I read somewhere that the last 6 digits of the vin should be stamped on the block. I'm not 100% sure where, but probably on the flat pad at the front of the block. Probably gone now from getting it decked.
Did you try to find the build sheet for the car. Sometimes the build sheet gets tossed in the car somewhere during assembly. I've heard that quite often they are underneath the back seat. The back seat bottom pops out quite easy. You might want to check there. That is where mine was. However, it was ripped in two and only half was there. I also heard that sometimes they are on top of the gas tank

I would definately try to look for it. If you could find it , that would tell you the options the car came with and if it is an original SS396 you would see either L34 or L78 on the build sheet.
Although that 11327 vin has me stumped as well. The cowl tags under the hood have been known to be wrong. Even mine doesn't match much the same as yours. Mine says 11427 under the hood and 11327 on the dash and title. However mine was a 6 cyl car and also a willowrun car LOL. The only other possibility I can think of is that maybe all the SS396 drivetrain got swapped to a 6 cyl car. But even that doesn't explain the 3600 lb weight on the title

And also if what you say is true about the original owner working for GM and buying it to race, I would say a 396 Nova would be a good chioce!