How to confirm year(s) of heavily-modified example?

[Tremelune]

I found a 1973 911T that I'm interested in, and the rear has SC flares and impact bumpers. Maybe a previous owner spent real money to make it look like a newer car, or maybe someone backdated the front of an 80s car and fudged the VIN. Both seem equally likely, depending on what year the modifications were done...

If I didn't know better, I'd say the engine looked like a 2.7 RS engine with MFI, but based on the, ah, prior decisions made, this would surprise me quite a bit. I'm much more familiar with 80s cars. Is there a reliable way to know which engine I'm looking at without taking it apart? Intakes and airboxes are easily changed. It's not currently running.

The interior is tired and could easily be half original, etc.

Basically, is there any way to look at a chassis and engine, without regard to the numbers on them, and figure out what they are? I've read many buyers guides, but most of them are casual descriptions of horsepower and transmission changes...

[davep]

What is not so easy to change are the stamped VIN in the front trunk, and the production # on the lower dash frame, behind the knee pad and below radio. I can find out if they match. Also get the paint code from the badge on the left door hinge post. As for the engine, the stamped #'s on the case will tell what the engine originally was. Then you have to strip it down to see what is in it. Every component will have some indication of what it is. Casting #'s are the most important. Numbers on the cylinders, the pistons, the rods and heads are important. All the #'s to be found on the MFI pump and throttle bodies will provide guidance. Strictly visual can lead you astray.